Partition it into 3 subsets, each with a distinct number of members ,
e.g . A=(1,2); B=(3,5,11,12) & C=(4,6,7,8,9,10).
Evaluate the sums of the members for each of the subsets, in our example:
Sa=3 ; Sb=31 & Sc=44;
F1 (product of the three sums) = Sa * Sb * Sc, i.e. 3*31*44 = 4092 in our example.
F2= Sa * Sb + Sc; equals to 93+44=137 in our case.
F3= d(Sa) +d(Sb) + d(Sc); where d(N) is the number of N's divisors.
So in our case F3=2+2+6 = 10.
The 3 independent tasks :
Executing the above procedures find the partitions of the main set, that provide maximum values for F1, F2 & F3.