There are several product combinations giving the 36 figure...
1,1,36 (sum = 38)
1,2,18 (21)
1,3,12 (16)
1,4,9 (14)
1,6,6 (13)
2,2,9 (13)
2,3,6 (11)
3,3,4 (10)
You need to use the other 2 pieces of info supplied to narrow it down to the correct answer.