Answer to Question #51666 in Economics for Dipankar sonowal

(a). First of all it is necessary to calculate total revenue as a
function of quantity.
TR = P * Q= (100 – 2q)*q = 100q – 2q^2
So, the marginal revenue function can be calculating as derivative
form total revenue:
MR = d TR /d Q = 100 – 4q
(b). If MR = 0
100 – 4q = 0
4q = 100
q = 25
P = 100 – 2q = 100 – 50 = 50