Answer:
t=2.14s
Step-by-step explanation:
Since it asks us for the time it takes from the moment it starts accelerating, the first 5 seconds of movement mentioned is irrelevant here.
Next it'd be simple just to use the kinematic equation involving distance, time, and velocity:
∆d=V₀t+at²/2
From here we can move the change in distance over and use the quadratic formula to solve for time.
My work is in the attachment. Comment with any questions.