Sum of expressions with if clause

I have a column with positive and negative values.

Positive values means number of goods sold, so to determine the profit, I multiply the quantity with the selling price.

Negative values mean number of goods not sold and worth nothing anymore, so to determine the cost, i multiply the quantity with the costprice.

The prices come in different columns

E.g.Quantity   |   Price   |   name   |   Profit     |    Cost

          5               12            A            5*12             0

          -3              5             B             0              -3*5

          ...              ...            ...            ...                 ...

 So profit and cost are calulated with expressions, which I can't do in the SQL query because of the if clause

But now I need to have a total of all of the profits and costs.

Any idea how to get the total in Report Builder?