A ferry boat headed directly away from the river bank is traveling at 3 km/h with respect to the water in a river flowing at 4 km/h. A passenger walks diagonally toward the stern of the boat with a speed of 1.39 m/s. The passenger's path is at an angle of 53.1 degrees toward the upstream direction from the length of the boat. What is the passenger's speed relative to the bank?
The Attempt at a Solution
I know the speeds form a triangle with leg lengths 3 and 4 and hypotenuse 5. I'm not sure where to go from there, though...