C. Rs.8000/-
Feedback A = Rs.20000/- per 12 months
B = Rs.30000/- per 18 months
C = Rs.40000/- per 24 months
= 20000 × 12 : 30000 × 18 : 40000 * 24
= 4 : 9 : 16
Total = 29 parts -----> Rs.14500/- (profit)
= 1 part ------> Rs.500/-
Then, C's share is
= 16 part = Rs.500/- × 16 parts = Rs.8000/-