The Dolan Corporation, a maker of small engines, determines that in 2012 the demand curve is: p=2000-50Q

where P is the price (in dollars) of an engine and Q is the number of engines sold per month.

a. to sell 20 engines per month, what price would Dolan have to charge?

b. If managers set a price of $500, how many engines will Dolan sell per month?

c. What is the price elasticity of demand if price equals $500?

d. At what price, if any, will the demand for Dolan's engines be of unitary elasticity?

Specifically, I need help with D, can you handwrite your work?