Effect of pressure gradient changes on laminar flow

Hi. If flow is laminar, what happens to flow when  the pressure gradient changes from 100mmhg (120-20mmhg) to 150mmhg (160-10)?
I was applying poiseuille's law however the answer choices are:
A) no change
B) decreases by 50%
C) increases 1.5x
D) increases 2x

I'm told the answer is C but if you consider the law and that flow is directly proportional to pressure gradient changes, I wouldn't think that C is the answer.
To double flow, pressure must quadruple, right?
I see that flow should increase but the answer (1.5x) puzzles me. It seems like an odd increase. Any thoughts!? Thanks!