Answer :
Well, to get the possible length you start with 6 in (0.5 feet) and add 5.5 feet multiple times. You could get 6, 11.5, 17, 22.5, 28, 33.5, 39, 44.5, 50, ...
Notice we missed the "35" option, which is, thus, not possible.
Notice we missed the "35" option, which is, thus, not possible.