Further Mechanics Impulse question

There's a question which I'm stuck on:

"A particle of mass 2kg is moving in a straight line on a smooth horizontal surface. When the speed of P is 3ms, P receives an impulse I Ns. Immediately after receiving the impulse, the speed of P is 9ms. As a result of the impulse, the direction of motion of P is deflected through an angle of 45 degrees"

It's asking to find the magnitude of the impulse. The mark scheme just says "Complete method to find the magnitude of I" and it's only worth 1 mark, so it's probably really simple. Would appreciate any help. Thanks!