A computer company advertises its computers in PC World, in PC Magazine, and on television. A survey of 730 customers finds that the numbers of customers who are familiar with the company's computers because of the different forms of advertising are as follows:

306, PC World 270, PC Magazine 390, television 120, PC World and PC Magazine 136, PC Magazine and television 140, PC World and television 81, all three sources

How many of the surveyed customers know about the computers because of:

(a) exactly one of these forms of advertising? customers (b) exactly two of these forms of advertising? customers (c) PC World and neither of the other two forms of advertising? customers