Lower tick price, higher attendance. How do I relate them?

A baseball team plays in a stadium that holds spectators. With the ticket price at , the average attendance at recent games has been . A market survey indicates that for every dollar the ticket price is lowered, attendance increases by .

(a)Find a function that models the revenue in terms of ticket price. (Let be the ticket price and be the revenue.)

So far, I have the following (but can't put it all together):

: tick price

: price reduction

: attendance

: Revenue in terms of attendance

Wrong letter ^ ^

How do I relate and

gives a smaller number for a bigger (wrong).

gives negative numbers (for example is a reduction means ), but at least it gets bigger as gets bigger.

I could do these two myself if I could do (a).

(b) Find the price that maximizes revenue from ticket sales.

(c) What ticket price is so high that no revenue is generated?