A proton initially has a v = 4.0i-2.0j+3.0k and then 4 sec later has a v (Vector) = -2.0i - 2.0j+5.0 k (in m/s). For that 4.0 second,
a) Determine the protons average acceleration, in unit v notation,
b) Determine the angle between average and the positive x axis?