C-11-Q153mediumsingle_mcqIf xp+q=yq+r=zr+p\dfrac{x}{p+q} = \dfrac{y}{q+r} = \dfrac{z}{r+p}p+qx=q+ry=r+pz, then by the sum rule each ratio equals—ax+y+z2(p+q+r)\dfrac{x+y+z}{2(p+q+r)}2(p+q+r)x+y+z