Please answer and explain each thoroughly. Thank you!

A store gets a shirt from a clothing manufacturer at a cost of $7 per shirt. The store has been offering this shirt at a price of $30, and at this price has been selling 180 shirts a month. The store plans to raise its price and estimates that for each $1 increase in price, 5 fewer shirts will be sold each month. Express the store's monthly profit from the sale of this shirt as a function of its selling price