If $\frac{dr}{dq}=\frac{900}{(q+2{)}^2},$ where $r$ is the total revenue of a product in dollars and $q$ is the number of units produced and sold, find $\frac{dr}{dm},$ where $m$ is the number of employees who are related to the level of production by the equation $q=10m,$ when $8$ employees are being employed.

A$.$ $$1\mathrm{.}34$ per employee

C$.$ $$1\mathrm{.}34$ per unit

B$.$ $$0\mathrm{.}13$ per employce

D$.$ $$0\mathrm{.}13$ per unit