I need help with these two please please thank you so much

17. 18. 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? . 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 dirction he's being pulled. The rescuer is pulling at a rate of 3 km/h. What is Bob's relative velocity to the ground? A triangle in R? has two sides represented by the vectors O4 = (1, 3,-1) and OB =(2, 4, 1). Determine the measures of the angles of the triangle. Explain