Day 15 - Count customers who purchased only Queso Cabrales on order

15 - # of Customers Who Purchased Only QC on Order = 
VAR _OrdersWithQC =
    CALCULATETABLE (
        VALUES ( Orders[OrderID] ),
        Products[ProductName] = "Queso Cabrales"
    )
VAR _ProdsByOrder =
    CALCULATETABLE (
        ADDCOLUMNS (
            SUMMARIZE ( Orders, Orders[CustomerID], Orders[OrderID] ),
            "@DistinctProds", CALCULATE ( DISTINCTCOUNT ( Orders[ProductID] ) )
        ),
        Orders[OrderID] IN _OrdersWithQC
    )
VAR _SingleItemOrdersWithQC =
    FILTER ( _ProdsByOrder, [@DistinctProds] = 1 )
VAR _CustomerIDs =
    SUMMARIZE ( _SingleItemOrdersWithQC, Orders[CustomerID] )
VAR _CountCustomers =
    COUNTROWS ( _CustomerIDs )
RETURN
    _CountCustomers