3. Assume that company A makes 75% of all electrocardiograph machines in the market, company B makes 20% of them, and company C makes the other 5%. The electrocardiographs machines made by company A have a 4% rate of defects, the company B machines have a 5% rate of defects, while the company C machines have a 8% rate of defects. (3) If a randomly selected electrocardiograph machine is tested and is found to be defective. Find the probability that it was made by company A. (b) Suppose we randomly select one electrocardiograph machine from the market. Find the prob- ability that it was made by company A and it is not defective