A61 kg zebra is traveling 8 m/s east. what is the zebra’s momentum?

Momentum = Mass × Velocity
                   = 61 × 8 
                   = 488 kg m/s east
                   = 500 kg m/s east

Momentum is a vector quantity which means it has a direction as well as a numerical value (fancy word for this is magnitude). This means the final answer should also be in the direction "east".
Furthermore due to the significant figures in the question, the final answer should also be given to 1 sig fig (500) but if you don't want to then I imagine 488 is acceptable. (It's like this because we don't know how accurate we can be with the final answer from the numbers in the question.)

My answer is opptionc, just check with anyone else