Chuck Sox makes wooden boxes in which to ship motorcycles. Chuck and his three employees invest a total of $20$ hours per day making the $120$ boxes.

a$)$ Their productivity $=6\mathrm{.}00$ 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 $220$ 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$).$