PROBABILITY Unit 2 Probability of Two or More Events TEXT
... Using the first letter of each drink and topping, it is easy to see that Cola (C)) could be
combined with any of the five toppings to give CH, CM, CS, CP, CT. Here 'CH' means
'Cola' drink and 'Ham' topping, etc.
Similarly, for Diet Cola (D), you have
DH, DM, DS, DP, DT
and for Orange (O)
OH, OM, OS, ...