Determine the least positive integer values of the following linear combinations ($x$ and $y$ are integers):
(a) $132x + 174y$
(b) $102x + 207y$
(c) $99x + 1008y$
(d) $666x + 3020y$
The least positive integer values of $ax + by$ is $\gcd(a,b)$.
(a) 6
(b) 3
(c) 9
(d) 2