A Dulac plants produces 500 cyperss packing boxes in 10-hour shifts. Due to higher demand, they have decided to operate three 8 hour shifts instead. They are now able to produce 600 boxes per day. What has happened to the production?

a. it has increased by 8.3%

b. it has increased by 50 sets/shifts

c. it has decreased by 9.1%

d. It has increased by 37.5 sets/hr

e. it has increased by 20%

explain your answer