Mass Spectrometer Question!

1.Some data obtained from the mass spectrum of a sample of carbon are given below.
Ion 12C+ 13C+
Absolute mass of one ion/g 1.993 x 10-23 2.158 x 10-23
Relative abundance/ % 98.9 1.1
Use the data to calculate the mass of one neutron, the RAM of 13C and the RAM of carbon in the sample.
You may neglect the mass of an electron.
Work out:
1.Mass of one neutron
2.RAM of 13C
3.RAM of carbon in the sample
I know how to work out the RAM form a mass spectrometer graph but cannot work this out. I presume you multiply the mass of one ion by relative abundance to (for the RAM questions) but then dont know the next step.
[tex]A_{r} of samples:\\
^{13}C:~~\frac{13 x 1.1}{100} = 1.43 x 10^{-1} = 0.143\\
Carbon:~~\frac{(12 x 98.9)~+~(13 x 1.1)}{(98.9 + 1.1)} = 12.011 = 12[/tex]
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