Rose Arena is the production manager for a manufacturing firm that produces buggy whips and other items. The annual demand for a particular buggy whip is 1,600 units. The holding cost is $2 per unit per year. The cost of setting up the production line is $25. There are 200 working days per year. Rose decided to produce 200 units each time she started production of the buggy whips. If it took her 4 days to produce the 200 units, what was her production rate?
a) 80 units/day
b) 60 units/day
c) 40 units/day
d) 100 units/day
e) none of the above