Answer:
1. The total incremental cost of making 65,000 units of RX5
Total Direct Material + Total direct Labour + Variable Overhead cost
Total Direct Material = 65,000 units * $5 = $325,000
Total Direct Labour = 65,000 units * $9 = $585,000
Variable Overhead cost = $65,000 * 10 = $650,000. $650,000 *(1- 80%) = $650,000 *20% = $130,000
Hence, The total incremental cost of making = $325,000 + $585,000 + $130,000 = $1,040,000
2. The total incremental cost of buying 65,000 units of RX5 =
The cost to buy the units = 65,000 units * $18 = $1,170,000
3. The company should be making the RX5 because the total cost of making the 65,000 unit of RX5 is lesser than cost of buying the 65,000 units of RX5