A 65.0 kg ice-skater standing on frictionless ice throws a 0.15 kg snowball horizontally at a speed of 32.0 m/s. at what speed does the skater move backward?
a. 3.0 x 10-1 m/s
c. 7.4 x 10-2 m/s
b. -7.4 x 10-2 m/s
d. 4.9 x 10-1 m/s