[SOLVED] Topic: Newton's third law

Jul 2010
A 2.0 kg bowl strikes the stationary ‘jack’, which has a mass of 1.0 kg, during a game of bowls. It is a head-on collision, and the acceleration of the jack is found to be 25 m s−2 north. What is the acceleration of the bowl?

I've calculated the answer to be 13 ms ^ -2 north; why does my textbook say south instead?