Factories A, B and C produce computers. Factory A produces 3 times as many computers as factory C, and factory B produces 6 times as many computers as factory C. The probability that a computer produced by factory A is defective is 0.02, the probability that a computer produced by factory B is defective is 0.025, and the probability that a computer produced by factory C is defective is 0.038.

A computer is selected at random and it is found to be defective. What is the probability it came from factory A?