Do OP to o perpendicular to BC and AD in q.

Because AD//BC

So AD is perpendicular to PQ.

So OQ =1/2ad =1/2a;

OP = 1/2BC = 1/2b；

So AE =1/2 (a+b);

So the perimeter of the quadrilateral AFED is:

2AE+2AD = 2 * 1/2(a+b)+2 * a = 3a+b。