Make sure to help me with B as well, thank you

Until recently, hamburgers at the city sports arena cost $3.30 each. The food concessionaire sold an average of 8,500 hamburgers on game night. When the price was raised to $3.90, hamburger sales dropped off to an average of 5,500 per night. (a) Assuming a linear demand curve, find the price of a hamburger that will maximize the nightly hamburger revenue. (b) If the concessionaire had fixed costs of $2,000 per night and the variable cost is $0.60 per hamburger, find the price of a hamburger that will maximize the nightly hamburger profit. (a) Assuming a linear demand curve, find the price of a hamburger that will maximize the nightly hamburger revenue. The hamburger price that will maximize the nightly hamburger revenue is $ (Round to the nearest cent as needed.)