Import the four-row CSV as Sales. Create each definition as a separate measure.
Format Margin % as a percentage with two decimal places.

Revenue =
SUMX ( Sales, Sales[Quantity] * Sales[UnitPrice] )

Cost =
SUMX ( Sales, Sales[Quantity] * Sales[UnitCost] )

Profit =
[Revenue] - [Cost]

Margin % =
DIVIDE ( [Profit], [Revenue] )

Customers =
DISTINCTCOUNT ( Sales[CustomerID] )

Customer-Category Memberships =
SUMX (
    VALUES ( Sales[Category] ),
    [Customers]
)

Qualified Revenue at Current Context =
IF ( [Revenue] >= 300, [Revenue], BLANK() )

Category Qualified Revenue =
SUMX (
    VALUES ( Sales[Category] ),
    VAR CategoryRevenue = [Revenue]
    RETURN
        IF ( CategoryRevenue >= 300, CategoryRevenue, BLANK() )
)