Answer with Explanation:
Requirement 1:
Incremental cost of making RX5:
Always remember that the direct costs are always incremental cost because these are the variable cost and will not be incurred if the decision is not taken related to making of the product RX5.
Incremental Cost of Making RX5:
Direct Material ($4 * 51,000 Units) $204,000
Direct Labor ($8 * 51,000 Units) $408,000
Variable Overheads ($9* 20% * 51,000 Units) $91,800
Total incremental cost of making 51000 units $703,800
Requirement 2:
Incremental Cost of Buying RX5:
Purchase Cost ($19 per Unit * 51,000 Units) $969,000
The total incremental cost of making 51000 units is $969,000
Requirement 3:
The Cost of buying is higher than making RX5, hence the company should Make RX5.