Result/summarization of multi-correct quiz to be sent to instructor and students

[jalote]

Currently multi-correct quiz summarization is sent as top answers and their frequency. Instead the result should be like this:

Option 1:
If N correct options, show:
How many ticked each of the options - as a pie chart, just like with single-correct answer.

Option 2:
If N correct options (N<=4), then summarization can be like this (for N=3):
% who selected all 3 correct options: xx
% who selected 2 correct options: xx
% who selected 1 correct opion: xx
% who selected 0 correct options: xx
....
This can be shown as pie chart. Note that the number of items depends on N.