Quick Question - Conservation of Momentum

[Dooga Blackrazor]

ball with a mass of 0.10 kg has a velocity of 7 m/s. It strikes a concrete wall perpendicularly and bounces straight back with velocity of 4 m/s. The change in the ball's momentum was equal to

Response Answer Choices
a. 0.30 kg m/s
b. 0.10 kg m/s
c. 0.40 kg m/s
d. 1.1 kg m/s

0.1 x 7 and .4 x .1 = .7 and .4 and subtracting them gives .30 kg m/s, correct?

 

[Dooga Blackrazor]

Nevermind, I found the answer (1.1). Silly mistake.