Consider:

$($a$)$ Stock trades for $$100$;

$($b$)$ Puts with exercise prices of $$90,$ $$100,$ and $$110$ trade at prices of $$3\mathrm{.}88,$ $$7\mathrm{.}94,$ and $$14\mathrm{.}77$ respectively.

If a person buys a $$90$ put and writes a $$110$ put, what is her maximum profit? Please answer correctly up to two decimal places.