The correct answer is (A):
The team completes the job in 4 days.
Since Amol needs 10 days to complete the job, in 4 days, he does 4/10th or 40% of the work.
Since Bimal needs 8 days to complete the job, in 4 days, he does 4/8th or 50% of the work.
Therefore, Kamal did 10% of the work and for doing 10% of the work, he gets 10% of the payment, i.e. Rs. 100.