The goal of this exercise is to find the molecular formula of unknown products that fits in the generale molecular formula:

C0-100 H0-100 N0-5 O0-10 F0-3
Cl0-3 Br0-3 S0-3.

We have here simulated spectra with a specified precision and analysis.

 

The way the molecule has been ionized is specified in the column 

 

From this mass you can find candidates but this is not enough because you can still have many molecular formula.

You may then use more information present in the spectrum like: