Concept: The question tests on the basics of Speed(Rates)
Solution:
Let the original speed = s. Therefore the new speed = 1.2 s
Let the original time = t. Therefore the new time = t - 20
Since distance is a constant, s1 * t1 = s2 * t2
s * t = 1.2s *(t - 20)
t = 1.2t - 24
0.2t = 24
t = 240 / 2 = 120 minutes = 2 hours
Option c