Situation:

120 people have to choose 3 choices from a list of 10.

i need to pick at random 2 from their choices (per person) and divide them (the 120 people) in 12 groups.

the 12 groups are: the list of 10 + 2 doubles from the list of 10 who were chosen the most.

Maximum size of a group is 20.

I have found this formula to choose 1 random choice out of 3 but am stuck for the next step:

=INDEX($A$2:$A$4,RANDBETWEEN(1,COUNTA($A$2:$A$4)),1)

where the choices of the first person are situated in A2, A3 and A4

Any ideas?