Let alpha,beta be the roots of the equation x^2-px+r=0 and alpha/2,2beta be the roots of the equation x^2-qx+r=0 then the value of r is

a) 2/9 (p-q)(2q-p)

b) 2/9 (q-p)(2p-q)

c) 2/9 (q-2p)(2q-p)

d) 2/9 (2p-q)(2q-p)