The problem is a work-efficiency problem where the efficiency of men and women varies. To complete the job, 50 men take 50 days, so the total work can be represented as 50*50 = 2500 man-days. Similarly, 80 women can complete the job in 50 days, which is 80*50 = 4000 woman-days.

Now, the contractor starts with 40 men and 48 women. He removes 5 men and 8 women every 10 days until the work is done. Therefore, in the first 10 days, (40 men + 48 women) work for 10 days amounting to 400 man-days and 480 woman-days. This process continues, with a decrease in manpower every 10 days.

As 2500 man-days work equals to 4000 woman-days work, one can convert the woman-days work to man-days work or vice versa, and calculate when the total work (2500 man-days or 4000 woman-days) is completed.

Doing so would reveal that the total work would be completed in 50 days, making option 2 the correct answer.