A building contractor buys 90 of his cement from supplier A

A building contractor buys 90% of his cement from supplier A and 10% from supplier B. A total of 70% of the bags from A arrive undamaged, and a total of 90% of the bags from B arrive undamaged. Find the probability that a damaged bag is from supplier A The probability is [ ].

total number of damaged bags = 90% * 0.3 + 10% * 0.1 = 28%

number of damaged bags from A = 90% * 0.3 = 27%