Answer:
C) both machines are equally productive.
Explanation:
Calculation for machine #1:
Production time: 8 hours - 2 hours = 6 hours
Parts produced: 6 hours × 100 parts/hour = 600 parts

Machine #2:
Production time: 8 hours - 0.5 hours = 7.5 hours
Parts produced: 7.5 hours × 80 parts/hour = 600 parts
Comparison:
Both machines produce the same number of parts in an eight-hour workday.
Therefore, the answer is C) both machines are equally productive.