12.(ii)     Check whether the following probabilities    and  
  are consistently defined  
 (ii)   
                
                  (ii)   Given, 
We know,
  P(A  B) = P(A)+ P(B) - P(A 
 B)
 0.8 = 0.5 + 0.4 - P(A 
 B)
 P(A 
 B) = 0.9 - 0.8 = 0.1
Therefore, P(A  B) < P(A) and P(A 
 B) < P(B) , which satisfies the condition.
Hence, the probabilities are consistently defined