Got an impulse question here that I wouldn't normally struggle with, however there's something about a change of direction and not sure what to do here?

A ball of mass 0.1 kg hits a wall at 15 m/s and rebounds at a speed of 5 m/s.

If the path of the ball's diverted by $\displaystyle \frac{\pi}{2}$ radians by the impact, find the magnitude of the impulse exerted on the ball by the wall.

$\displaystyle I = m(v_2 - v_1)$

$\displaystyle I = 0.1(-5 - 15) = -20$, so the magnitude of the impulse would be $\displaystyle 20 Ns$?

Think that's right anyway. However I'm not sure how I'd solve it with the change of direction involved?

Thanks in advance