(5,12,13) is a right triangle and can be constructed. All the others do not satisfy the triangle inequality, i.e. the sum of two short sides must exceed the long side in order for the triangle to be constructed. Examples: 2+11<15, so no 3+7<11, so no 4+8<15, so no but 5+12>13 so yes, it can be constructed.
I'm just gonna tell you the answer and you'll have to show the work on your own. A penny doubled everyday for a month equals a little over $5 million dollars. So you would want to go with the second option.
