Does anyone knows standard way to solve this?
Let me share how I got 20.
First I figured the diameter is 4 and hight is 12
so in order to maximize the storage utilization 14 has to be used as hight of the box and 16X20 has to used as length and width. so we have an are of 16X20 to be filled up by cylinder with will be taking as much as 4X4 area.
so (16X20)/(4X4) = 20 cans.
still you have 2X14 free areas but you can not fit anything there.
So 20 is the right answer.