please detail

QUESTION 1 You run a firm that sells custom t-shirts over the Internet. You want to know how changing prices will affect your firm's revenues and profits. To do this, you decide to run a market experiment. You raise your price from your standard price of $18 to $20 When you do this, your weekly sales fall from 4,500 t-shirts per week to 3,500 t-shirts per week. Assuming that your firm's demand function is linear ( Q(P)=a-bp), estimate your demand function. What is the "b" parameter QUESTION 2 What is the "a" parameter