As I was riding into the cold, wet north wind this morning it occurred to me (that I forgot mention) that you'll also need to know the size of wheels and what kind terrain (gravel, streets, dirt, etc.) they intend to ride on. It's also worth considering what style of bike they're riding. (mtb vs road vs beach cruiser and so on)

It would also be worth your time to visit several existing websites where fg bikes are sold and see what kind of gearing options, if any, they give. Depending on the size, and intended audience, of the seller they're likely to just go with whatever they can get cheaply and in bulk.

In my mind a "pro" / experienced cyclist mode would be just like most of the existing calculators where you can put in your wheel/tire size, chainring size, and cog size along with the other usual options and then just give back the gear inches, gain ratio, speed vs. cadence or whatever they're looking for. (My favorite http://sheldonbrown.com/gears/ )

One more thought, unless your professor is a dedicated cyclist s/he won't really know if the recommended gearing (the output) from your helper is correct vs. the inputs given. Most likely s/he won't care anyway. As long as your program actually runs and produces the expected output for the given input and doesn't produce any unexplained errors or other failures, you'll probably be fine. (well... depending also on whether this is a semester long project or one of several small projects throughout the semester)

You're welcome.

(CSE, not bikes, btw.)