On a river there is the mid-point between initial and final on the same bank of the river. A boat can go from initial to the midpoint and back in 15 hours and from initial to final in 18 hours 30 min. How much time it will take to go back to the initial from the final point?
1
9 hr 15 min
2
11 hr 30 min
3
9 hr 10 min
4
9 hr 9 min