A boat takes a total time of three hours to travel downstream from P and Q and upstream back from Q to P. What is the speed of the boat in still water?
I. The speed of the river current is 1 km per hour.
II. The distance between P and Q is 4 km.
a) I alone sufficient while II alone not sufficient to answer
b) II alone sufficient while I alone not sufficient to answer
c) Either I or II alone sufficient to answer
d) Both I and II are not sufficient to answer
e) Both I and II are necessary to answer