diff --git a/exercises/ex04-marketplace/loosely-coupled-marketplace/src/lib.rs b/exercises/ex04-marketplace/loosely-coupled-marketplace/src/lib.rs
index 29fde5a..09aa3cb 100644
--- a/exercises/ex04-marketplace/loosely-coupled-marketplace/src/lib.rs
+++ b/exercises/ex04-marketplace/loosely-coupled-marketplace/src/lib.rs
@@ -85,9 +85,7 @@ pub mod pallet {
 			let origin = ensure_signed(origin)?;
 
 			ensure!(amount > 0, Error::<T>::ZeroAmount);
-			let owned: u128 = todo!(
-				"get the amount of this specific NFT owned by the seller, through the Resource type and its Sellable trait"
-			);
+			let owned = T::Resource::amount_owned(nft_id, origin.clone());
 			ensure!(owned >= amount, Error::<T>::NotEnoughOwned);
 
 			ResourcesForSale::<T>::insert(nft_id, origin.clone(), SaleData { price, amount });
@@ -107,9 +105,7 @@ pub mod pallet {
 			let buyer = ensure_signed(origin)?;
 
 			let sale_data = ResourcesForSale::<T>::get(nft_id, seller.clone());
-			let owned = todo!(
-				"get the amount of this specific NFT owned by the seller, through the Resource type and its Sellable trait"
-			);
+			let owned = T::Resource::amount_owned(nft_id, seller.clone());
 
 			ensure!(amount <= sale_data.amount, Error::<T>::NotEnoughInSale);
 			ensure!(sale_data.amount <= owned, Error::<T>::NotEnoughOwned);
@@ -119,9 +115,9 @@ pub mod pallet {
 				.checked_mul(&amount.checked_into().ok_or(Error::<T>::Overflow)?)
 				.ok_or(Error::<T>::Overflow)?;
 
-			todo!("transfer the amount of currency owed from the buyer to the seller");
+			T::Currency::transfer(&buyer, &seller, total_to_pay, KeepAlive)?;
 
-			todo!("transfer amount of nft_id from the seller to the buyer");
+			T::Resource::transfer(nft_id, seller.clone(), buyer.clone(), amount);
 
 			if amount == sale_data.amount {
 				ResourcesForSale::<T>::remove(nft_id, seller.clone());
diff --git a/exercises/ex04-marketplace/marketplace-nfts/src/lib.rs b/exercises/ex04-marketplace/marketplace-nfts/src/lib.rs
index a8d9e78..0e843ea 100644
--- a/exercises/ex04-marketplace/marketplace-nfts/src/lib.rs
+++ b/exercises/ex04-marketplace/marketplace-nfts/src/lib.rs
@@ -208,10 +208,10 @@ impl<T: Config> Pallet<T> {
 
 impl<T: Config> Sellable<T::AccountId, T::NFTId> for Pallet<T> {
 	fn amount_owned(nft_id: T::NFTId, account: T::AccountId) -> u128 {
-		todo!("return the amount of nft_id owned by account")
+		Self::account(nft_id, account)
 	}
 
 	fn transfer(nft_id: T::NFTId, from: T::AccountId, to: T::AccountId, amount: u128) -> u128 {
-		todo!("do the transfer")
+		Self::unchecked_transfer(nft_id, from, to, amount)
 	}
 }
diff --git a/exercises/ex04-marketplace/tightly-coupled-marketplace/src/lib.rs b/exercises/ex04-marketplace/tightly-coupled-marketplace/src/lib.rs
index e9766d5..74b913f 100644
--- a/exercises/ex04-marketplace/tightly-coupled-marketplace/src/lib.rs
+++ b/exercises/ex04-marketplace/tightly-coupled-marketplace/src/lib.rs
@@ -23,8 +23,9 @@ pub mod pallet {
 	use frame_system::{ensure_signed, pallet_prelude::*};
 
 	#[pallet::config]
-	pub trait Config: frame_system::Config + scale_info::TypeInfo {
-		todo!("add a dependency on pallet_marketplace_nft on the previous line");
+	pub trait Config:
+		frame_system::Config + scale_info::TypeInfo + pallet_marketplace_nfts::Config
+	{
 		type Event: From<Event<Self>> + IsType<<Self as frame_system::Config>::Event>;
 		type Currency: Currency<Self::AccountId>;
 	}
@@ -75,7 +76,7 @@ pub mod pallet {
 			let origin = ensure_signed(origin)?;
 
 			ensure!(amount > 0, Error::<T>::ZeroAmount);
-			let owned = todo!("get the amount owned from the pallet_nft account storage");
+			let owned = pallet_marketplace_nfts::Pallet::<T>::account(nft_id, origin.clone());
 			ensure!(owned >= amount, Error::<T>::NotEnoughOwned);
 
 			NFTsForSale::<T>::insert(nft_id, origin.clone(), SaleData { price, amount });
@@ -95,7 +96,7 @@ pub mod pallet {
 			let buyer = ensure_signed(origin)?;
 
 			let sale_data = NFTsForSale::<T>::get(nft_id, seller.clone());
-			let owned = todo!("get the amount owned from the pallet_nft account storage");
+			let owned = pallet_marketplace_nfts::Pallet::<T>::account(nft_id, seller.clone());
 
 			ensure!(amount <= sale_data.amount, Error::<T>::NotEnoughInSale);
 			ensure!(sale_data.amount <= owned, Error::<T>::NotEnoughOwned);
@@ -107,7 +108,12 @@ pub mod pallet {
 
 			<T as pallet::Config>::Currency::transfer(&buyer, &seller, total_to_pay, KeepAlive)?;
 
-			todo!("call the pallet_marketplace_nft transfer function");
+			pallet_marketplace_nfts::Pallet::<T>::unchecked_transfer(
+				nft_id,
+				seller.clone(),
+				buyer.clone(),
+				amount,
+			);
 
 			if amount == sale_data.amount {
 				NFTsForSale::<T>::remove(nft_id, seller.clone());