A company that manufactures tennis balls operates three shifts each day. Based on past experience, it is known that a percentage of the balls produced will be defective. The following table shows the percentage produced on each shift and the percentage of defectives in each shift:

Shift Percentage Percentage

Produced of Defectives

1 30% 10%

2 50% 15%

3 20% 20%

If a tennis ball is chosen at random and found to be defective, what is the probability that it was produced on the first shift?