A child in danger of drowning in a river is being carried downstream by a current that flows uniformly at a speed of `2.5 km//h.` The child is 0.6 km from shore and 0.8 km upstream of a boat landing when a rescue boat sets out. If the boat proceeds at its maximum speed of `20 km//h` with respect to the water, what angle does the boat velocity v make with the shore? How long will it take boat to reach the child?