Answer: N = 4845
Therefore, the number of different combinations of programs that can be run at the same time is 4845.
Step-by-step explanation:
In combination, the order of the programs does not matter.
nCr = n!/r!(n-r)!
For the case above we want to determine the number of combinations of 20 programs on a 4 cores computer.
N = 20C4 = 20!/4!(20-4)!
N = 20!/4!16!
N = (20×19×18×17×16!)/(4!×16!)
N = 4845
