Hello, I would like some help to solve this question please.

1. (20 pts) There are three consumers, namely A, B and C, who are willing to pay for a public good. Their individual's inverse demand functions are given by PA = 25-1/20, PB = 70 - Q and Pc = 80 - Q, respectively. Derive algebraically and graphically the aggregate demand for this public good. Indicate intercepts and kink point(s). Calculate the total benefits for consumer A at a quantity Q = 10