Answer:
$5
Explanation:
Marginal cost also known as the incremental cost is defined as the incremental cost of producing an additional unit of a product or service , calculated by dividing the total increase in cost by increased number of goods produced.( change in cost /change in unit).
It is used to measure and evaluate an increase or decrease in the cost of production.
Workings
Additional cost - $75
Total increase in daily delivery = (75-60)=15
Marginal cost = 75/15 = %5