\(P(A\mid B)P(B)=P(AB)\)
\(P(B)=\sum_{i=1}^n P(A_i)P(B\mid A_i)\)
\(P(A_i\mid B)=\dfrac{P(B\mid A_i)P(A_i)}{\sum_{i=1}^nP(A_i)P(B\mid A_i)}\)