The height of a mountain above sea level at point (x, y) is given by f(x, y). A mountain climber standing at a point P notices that the slope if moving towards the east is – 1/2 and the slope towards...

The height of a mountain above sea level at point (x, y) is given by f(x, y). A mountain climber standing at a point
P
notices that the slope if moving towards the east is – 1/2 and the slope towards the north is -1/4. In which direction should the mountaineer move if he wants to descend the mountain in the fastest time?