Can you guys help me in this ques

Suppose a function f 2 R3 > IR has total derivative Daf= [13 1 11] Suppose a particle P moves through a = (20, 2, 10) with speed 2. Find the velocity vector V so that P experiences maximum rate of increase of f at the instant of passing through a. v = |_l;l|_l What rate of change of fdoes the particle experience at the instant of passing through a with velocity v