P(B|A)=1-A(5,4)/A(6,4)=1-5*4*3*2/(6*5*4*3)=1-1/3=2/3
P(A|B)=(A(6,4)-A(5,4))/(6^4-5^4)=(6*5*4*3-5*4*3*2)/(1296-625)=240/671