A.1/12λb*b*b B.1/36λb*b*b C.1/48λ(b1+b2)(b1*b1+b2*b2) D.1/48λb*b*b
A.1/9λb*b*b B.1/12λb*b*b C.1/36λb*b*b D.1/48λb*b*b
A.1/12λb*b*b B.1/16λb*b*b C.1/36λb*b*b D.1/48λb*b*b