the factors of 60 are 2,3,4,6,10,15,20,30
so, if Calvin has c onions (c >= 7),
c must be a factor of 60, since c and some multiple of c add to 60.
The maximum for Ken means the minimum for Calvin.
So, if Calvin has 10, then Ken has 50, the max.
There are no other factors of 60 less than 10, but greater than 7.