It's a long time since this was posted. I don't know why you didn't ask me directly. There is an oversight in exercise 2. The main term on the RHS in question 2 should be gcd(a_1,a_2,a_3)J(n)\frak S. One has to use intervals of length 1/gcd(a_1,a_2,a_3).
Bob Vaughan
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