Question 1 was marked out of 4: 2 marks for correct Fs, 1 mark for a graph, 1 mark for suggesting that something happens at +/- 8 +/- 2 kHz (exactly what happens in that range would depend on your assumptions).
Question 5 was marked out of 10: 2 marks were given for each of the 4 lags (2 if the result was correct and the work was shown, 1 if the result was correct but didn't show the work, 0 if the result was wrong). 2 marks were given for a plot showing the right values, 1 if it had some mistakes, 0 if there was no plot.
1 mark was deducted for not including an indication of the Matlab commands used to generate the plot.