Need help! I am completely lost!

Hi!

I've been asked by my university to run a program in C language, i've been trying many time but i cannot do it right!
Does anyone have and idea how should i do it? how to begin and which formulas to use?

It is a group project, I only need to do this part:
(Write the functions that calculate the fuel use. Of course, you won't have the aircraft data yet. Instead, make up a very simple set of data. The data should be in the same format as you're expecting from Pair A, as you'll be using the same function to work on the real data.)

Here is the exercise:
Write a program to the following specification.
1. The program shall prompt the user to input a four character ICAO aircraft type identifier code (e.g. Airbus A330-200 = A332, Boeing 767-400 = B764).
2. If a performance data file for that aircraft can be found, the program shall read the True Air Speed (TAS), rates of climb or descent (ROCD) and fuel flow rates for all available flight levels (altitudes). See Appendix A for details of the BADA performance file format.
3. Ifnomatchingperformancedatafilecanbefound,theprogramshallinformtheuser and terminate without error.
4. The program shall prompt the user to input the length to be flown in Nautical Miles (NM).
5. The program shall display the total fuel used in kg for twenty choices of cruising altitude, between 1000ft and the aircraft's maximum altitude, in a neatly formatted table.
6. The program shall determine fuel use by integrating consumption over not less than 20 steps for the climb and 20 steps for the descent. The program shall interpolate between the points available in the BADA file. See Appendix B for details on how to integrate fuel use.
7. The program shall display the cruising altitude that achieves the smallest total fuel use, calculated by the Golden Section minimization using not less than 20 iterations. See Appendix C for details on how this is done.

Thank you very much!!! !!!