If the demand function is

P = 60 − Q

find an expression for TR in terms of Q.

(1) Differentiate TR with respect to Q to find a general expression for MR in terms of Q. Hence write down the exact value of MR at Q = 50.

(2) Calculate the value of TR when

(a) Q = 50

(b) Q = 51

And hence confirm that the 1 unit increase approach gives a reasonable approximation to the exact value of MR obtained in part (1).