Correct option is C
Given:
S completes the task in 50 days
T completes the task in 40 days
M completes the task in 30 days
Work pattern:
Work starts on Monday
S works every day
T works Monday, Wednesday, Friday
M works Saturday, Sunday
Solution:
S works 7 days → 7×501=507
T works 3 days → 3×401=403
M works 2 days → 2×301=302=151
Total weekly work :
=507+403+151
=60084+45+40=600169
Time = 6001691=169600≈3.55 weeks
Thus, Work will be completed between 3 to 4 weeks.
Alternate Solution: