Correct Answer - Option 3 : Rs.24,000
Time take by A to complete the work = 25 days
Time taken by B to complete the work = 25 × (100/125) = 20 days
C's one day work = (1/25 + 1/20) × (100/180) = (9/100) × (100/180) = 1/20
∴ Time taken by C to complete the work = 20 day
Ratio of time taken by A, B and C = 25 ∶ 20 ∶ 20 = 5 ∶ 4 ∶ 4
⇒ Efficiency of A, B and C = 4 ∶ 5 ∶ 5
Weekly income of the three workers = Rs.19,600
⇒ Daily income of the workers = 19,600/7 = Rs.2800
∴ Daily income of A = (4/14) × 2800 = Rs.800
⇒ Monthly income of A = 800 × 30 = Rs.24000