A ferry is crossing a river. The ferry is headed due north with a speed of 4.8 m/s relative to the water. If the river's velocity is 2.1 m/s east, what will the ferry's velocity be relative to an on-shore observer? Select one:

a.5.2 m/s at 24° E of N
b. 4.9 m/s at 28° E of N
c. 4.9 m/s at 62° E of N
d. 5.2 m/s at 28° E