Used Tractor Values

Joey bought a new tractor for use in his landscaping business. He expects that the use of the tractor will generate 4500 dollors of revenue in the first year with an increase in revenue of 400 dollars per year for subsequent years. If the tractors useful lifetime is 7 years how much revenue will joes receive from the use of the tractor

The John Deere Company has found that the revenue from sales of heavy-duty tractors is a function of the unit price p (in dollars) that it charges. If the revenue R is
R(p)= -1/2p*2+1900p
What unit price p (in dollars) should be charged to maximize revenue? What is the maximum revenue?
PS: (*) means exponent