Gas chromotography-mass spec percent composition

So I conducted a lab where I prepared 4 standard solutions of diesel/biodisel mixtures and then analyzed a diesel/biodeisel sample of unknown composition.

We put all the samples into a GC-MS instrument (gas chromotograph-mass spectrograph).

I have a gas chromatogram for all samples and then a mass spectrum of the highest two peaks in each chromatogram.

Both the chromatograms and mass specs are in terms of relative abundance.

I am supposed to determine (i was told I could estimate) the percent composition of biodiesel in the unknown.

Can someone help me understand how I can use the gas chromatograms and mass specs to figure this out?

Can I just take the relative abundance of (whatever I determine to be) the biodiesel peak over the sum of the relative abundances of all other peaks?

What can the mass spec tell me? Is it just to help me figure out which peak is biodiesel and which is diesel?

I am not understanding this!
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