There are four bo

Let A : Ball drawn from bag A

B : Ball is drawn from bag B

C : Ball is drawn from bag C

D : Ball is drawn from bag D

BB : Black ball

WB : White ball

RB : Red ball

Assuming all boxes have an equal probability for picking i.e.

We want to find P(A|RB), i.e. probability of selected red ball is from box A

Conclusion: Therefore, the probability of selected red ball is from box A is