Chuck Sox makes wooden boxes in which to ship motorcycles. Chuck and his three employees invest a total of $40$ hours per day making the $200$ boxes.

a$)$ Their productivity $=5$ boxes$/$hour $($round your response to two decimal places$).$

Chuck and his employees have discussed redesigning the process to improve efficiency. Suppose they can increase the rate to $400$ boxes per day.

b$)$ Their new productivity $=,$ boxes$/$hour $($round your response to two decimal places$).$

c$)$ The unit increase in productivity is boxes$/$hour $($round your response to two decimal places$).$