Find the directions in which the function increases and decreases most rapidly at P₀. Then find the derivatives of the function in these directions.
f(x, y, z) = x/y - yz, P₀(2, 1, 3)

The directions are:
a) Increase in x, decrease in y
b) Decrease in x, increase in y
c) Increase in x, increase in y
d) Decrease in x, decrease in y