Bob can swim at a rate of 5 km/h. He is in a river that is flowing at a rate of 9 km/h.

a. If bob swims upstream, what is his relative velocity to the ground?

b. If bob swims downstream, what is his relative velocity to the ground?

c. Someone decides to help bob out of the water with a rope. Bob swims across the river(perpendicular to the flow of water) in the same direction he's being pulled. The rescuer is pulling at a rate of 3 km/h. What is Bob's relative velocity to the ground?