Concept: The question tests on the basics of Rates(Time and Work)
Solution:
Using the concept of Man Days where M1T1/W1=M2T2/W2
Let M1 = M, then M2 = 2M
T1 = 12 Days
Let W1 = W, then W2 = 0.5W
Therefore, we have M∗12/W=2*M∗T/0.5W
12M = 4MT
T = 3
Option E