Answer:
At t = 0 S = 0
S = 3 * 3^3 - 20 * 3^2 + 40 * 3 after 3 sec
S = 3 * 27 - 20 * 9 + 120 = 21 after 3 sec
v = ds/dt = 9 * t^2 - 40 * t + 40 = 9 * 9 - 40 * 3 + 40 = 1
ds/dt = 9 t^2 - 40 t + 40 v at any time
If zero = 9 t^2 - 40 t + 40 then you need to solve the quadratic for t
a = ds^2 / dt^2 = dv /dt = 18 t - 40 for the acceleration at any time
At t = zero (the initial acceleration) a = -40