A computer store buys a computer system at a cost of $640.50. The selling price was set at $854, but after a year the computer did not sell. The store then advertises a 25% markdown on the $854 computer system. Find the sale price.

If the angle bisectors of a pair of opposite angles of a quadrilateral are the opposite sides of a parallelogram formed by the two angle bisectors and two sides of the quadrilateral, is the quadrilateral always a parallelogram? explain your answer.