=+d. Substitute y1z, w, r2 into the first order condition that contains r. Then manipulate the resulting equation until you have it in the form az2 1 bz 1 c (where the terms

a, b, and c may be functions of w, r,

a, and p). (Hint: It is helpful to multiply both sides of the equation by r.) The quadratic formula then allows you to derive two “solutions” for z. Choose the one that uses the negative rather than the positive sign in the quadratic formula as your “true” solution z*1a, p, w, r2.