Concept: The question tests on the basics of Rates(Time and Work)
Solution:
Using the concept of Man Days, we have M1T1/W1=M2T2/W2
Let the number of days taken = x
M1 = Those doing the work = 49
T1 = Time Taken = 6.5 * 8 = 52 hours
M2 = 196
T2 = x hours * 5 = 5x
Then 49 * 52 = 196 * 5x
x = 2.6 days
Option C