Aman wishes to travel due north in order to cross a river 5 km wide flowing due east at 3 km/hr. if he can row at 10 km/hr in still water find
(a) the direction in which he must head his boat in order to get to his destination directly opposite his starting point
(b) the resultant velocity of the boat in the river
(c) the time taken to cross
(d) how far from his destination he would land if he ignorantly steers northward