To count impulse you will need more information as it was different with time. In this question, there are two balls with different mass and velocity, thus they have different momentum. I will assume you are asking about the momentum
The momentum of ball 1 should be:
momentum 1= mass1 * velocity1
momentum 1= 2kg * 10m/s= 20kg m/s
The momentum of ball 2 should be:
momentum 2= mass2 * velocity2
momentum 2= 1.5kg * 20 m/s= 30kg m/s
The answer would be: 1.5kg ball because it was travelling faster
