Answer:
t=17.838s
Explanation:
The displacement is divided in two sections, the first is a section with constant acceleration, and the second one with constant velocity. Let's consider the first:
The acceleration is, by definition:

So, the velocity can be obtained by integrating this expression:

The velocity is, by definition:
, so
.
Do x=11 in order to find the time spent.

At this time the velocity is: 
This velocity remains constant in the section 2, so for that section the movement equation is:

The left distance is 89 meters, and the velocity is
, so:

So, the total time is 14.303+3.5355s=17.838s