Greatest Common Divisors

Find a set of four positive integers,
such that the greatest common divisor (GCD)
of each pair of integers is a unique number.
(There are six different pairs.)

Find a set of four positive integers, such that the GCD of each subset of
three
integers is a unique number.

Find a set of five positive integers, such that the GCD of each pair of
integers is a unique number.

Find a set of five positive integers, such that the GCD of each subset
of three integers is a unique number.

Find a set of five positive integers, such that the GCD of each subset
of four integers is a unique number.
Repeat the above with the requirement that each GCD found must be
greater than 1.
In each case, try to find the set with the smallest sum.
Source: Original.
Solution
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