Answer:  These are two ways to calculate P[A|B].

Question:  What are two of the following:

   P[A Ç B] / P[B]

   P[A Ç B] / (P[A Ç B] + P[A^C Ç B])

   P[B | A] P[A] / P[B]

   P[B | A] P[A] / (P[A Ç B] + P[A^C Ç B])

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