Analyze the logical forms of the following statements: (a) 3 is a common divisor of 6, 9, and 15. (Note: You did this in exercise 2 of Section 1.1, but you should be able to give a better answer now.) (b) x is divisible by both 2 and 3 but not 4. (c) x and y are natural numbers, and exactly one of them is prime