The Populus Tremula Plant has just implemented a process improvement, which resulted $20\%$

increase in output with less material, but it requires three additional workers. Under the old process,

seven workers could produce $60$ units per hour.

Labor costs are $$30/$hour$.$ Material input was

previously $$25/$unit and is $$20/$unit for the new process. Overhead is estimated to be $1\mathrm{.}2$ times

direct labor cost.

Finished products sell for $$45$ each.

Calculate the increase in productivity

associated with the process improvement.