If the inverse demand function is:
p = 50 - 0.5Q,
a. What is the price elasticity of demand and revenue at Q = 88?

-0.136 and $528

Explanation:

Given that

p = 50 - 0.5Q

where,

Q = 88

So, p equals to

= 50 - 0.5 × 88

= 50 - 44

= $6  

As it is mentioned that

p = 50 - 0.5Q

0.5Q = 50 - p

Q = 100 - 2p

And we know that

Price elasticity of demand is

= Percentage Change in quantity demanded ÷ Percentage Change in price

So,

= -2 × (6 ÷ 88)

= -0.136

And, the revenue is

= Price × Quantity

= $6 × 88

= $528

it's obviously d. it could be c though.