$1-3.$ A small company manufactures bicycles. The revenue function is $R(x)=90x-x^2$ and the cost function is $C(x)=10+340x+2\mathrm{.}75x^2+(\frac{1}{60})x^3,$ where $x$ is the number of bicycles produced each week and $R(x)$ and $C(x)$ are in dollars.

Find the maximum revenue and where it occurs. $(8$ points$)$

Find the profit function $P(x).(4$ points$)$

Find where the profit function is increasing.$($I am having trouble with the last part of this question$)$