Answer:
The answer is 63.6

Explanation:
In order to determine the area of the quadrilateral, we have to know the values of its sides. The area of the quadrilateral is:

a= length of the quadrilateral
b=width of the quadrilateral
We know the area and the width of the quadrilateral, so we can determine its length:

Then, the perimeter of the quadrilateral is:
P=2*a+2*b
P=2*15+2*16.8
P=63.6
Finally, the perimeter is 63.6
