Question

A unit square is drawn in the Cartesian plane with vertices at (0,0),(0,1),(1,0),(1,1). Two points P,Q are chosen uniformly at random, P from the boundary of the square and Q from the interior of the square. The line L1 through P and Q is drawn. The probability that the points (0,0) and (1,1) are both on the same side of L1 can be expressed as a/b where a and b are coprime positive integers. What is the value of a+b?