20. (10 points) Alum manufactures aluminum strips for commercial building construction. Alum makes three types of strips 1/8 inch, 1/4 inch and 1/2 inch. Actual and Budget operating data by product for the most recent reporting period are as follows: ACTUAL BUDGET 1/8 1/4 1/2 1/8 1/4 1/2 Sales-# units 84 126 210 200 100 200 Price/unit $25 $32 $45 $20 $30 $40 Var. Cost / unit $16 $18 $22 $15 $17 $20 a. Calculate the sales-mix variance for each product and in total.