Hi, for the last question, I think this is a valid approach… if someone can review this it would be great. Basically to have 4 odd factors only, and no even factors, we want our number to be multiple of two odd prime numbers. If the prime factorization of the number is of the form p^1q^1, where p and q are odd numbers, it will ensure that we have exactly 2x2=4 odd numbers. So I listed up all possible prime numbers, 3 to 31. Beyond 31, 37x3 is greater than 100 and 3 is the least odd prime we got so no point exploring. Then for each prime we enlist the possible odd prime multipliers such that the result is smaller than 100. We only look at smaller primes to multiply the current prime with in order to avoid repetitions. Adding all such possible pair we get 17. Here is a walk through of what I did:

Sounds fine to me.

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