probability of the product of numbers

1) If two of the four expressions x+y, x+5y, x-y, and 5x-y are chosen at random, what is the probability that their product will be of the form of x^2 - (by)^2, where b is an integer?

A. 1/2
B. 1/3
C. 1/4
D. 1/5
E. 1/6

2) A circular medallion made of a circular piece of colored glass is surrounded by a metal frame. If the radius of the medallion is r centimeters and the width of the metal frame is s centimeters, then in terms of s and r, what is the area of the metal frame, in square centimeters?

A. pi(r-s)^2
B. pi(r^2 - s^2)
C. 2pi(r-s)
D. pi*r(2r-s)
E. pi*s(2r-s)

All OAs will be posted. Thanks