q=D(x)=1080-18x

the weekly sales of t-shirts is given by the function q=D(x)=1080-18x. where the variable q represents the number of t-shirts sold when the unit price is p.

a)Calculate the elasticity of demand when the price is $20 per shirt

b)is the demand at the price p=20 elastic or inelastic?

c)when the price is p=20, what would you need to do to the price(lower or raise) to increase revenue?

d)what price for a t-shirt will maximize revenue ?