Please answer all parts!

The codeine (C18H21NO3) content in Nurofen Plus tablets was quantifid by gas chromatography mass spectrometry (GC/MS) with an ion trap mass analyser using codeine-d6 internal standard. The following procedure was used to prepare the samples to be analysed: Stock codeine standard contained 20mg of codeine in 100mL of ethyl acetate. Internal standard (IS) solution contained 100mg of codeine-d6 in 100 mL of ethyl acetate. Two Nurofen Plus tablets were weighted and crushed and added to 100 mL of ethyl acetate in a volumetric flask. 2.5mL of this solution was added to 2mL of internal standard solution and made up to 10mL with ethyl acetate in a volumetric flask. (i) Outline the principles of operation of an 'ion trap' mass analyser. [10 marks ] (ii) Using the data provided, calculate the amount of codeine, in mg, per Nurofen Plus tablet. [15 marks] (iii) Briefly describe how GC-MS is used for the qualitative analysis of codeine, C18H21NO3 and codeine-d6, C18H15D6NO3. [5 marks]