Which of the following numbers will replace the question mark (?) in the given series?

27, 54, 42, 84, 72, 144, ?

​Given:

27, 54, 42, 84, 72, 144, ?

Given series contains two series.

Series 1: 27, 42, 72, ?

Logic: +15, +30, +60 pattern follows

27+15=42

42+30=72

Series 2: 54, 84, 144

Logic: +30, +60 pattern follows

54+30=84

84+60=144

Thus, correct option is (a).