Range = 2
There are several sets wirh range 2 and min max number pairs as: (1,3) (2,4), (3,5).....
Set1: (2,4) i.e, Set with min = 2 and max = 4 can have, 0 students contributing 3.
x=number of contributing 2
y= number of people contributing 4
2x+4y = 28
x+y = 10
=> x = 6 & y = 4
So there can be 0 boys contributing 3. (I: 0 is POSSIBLE)
x = number of contributing 1
y = number of people contributing 3
x + 3y = 28
x + y = 10
=> x = 1, y=9
Therefor 9 boys can be contributing 3 (III: 9 is POSSIBLE)
Others don't satisfy all the three conditions.
What's the source joemama. I had to scratch my head several times and still I am not sure about the answer
"To dream anything that you want to dream, that is the beauty of the human mind. To do anything that you want to do, that is the strength of the human will. To trust yourself, to test your limits, that is the courage to succeed."
- Bernard Edmonds