Consider a box containing 5 radio tubes selected at random from the output of a machine, which is known to be 20% defective on the average (that is, the probability that an item produced by the machine will be defective is 0.2). Suppose that 2 tubes are selected at random from the box and tested. You are informed that at least 1 of the tubes selected is defective; what is the probability that both tubes will be defective?