Answer:
4845 different combinations of programs
Explanation:
A combination is an arrangement where order is NOT important.
In this case, the number of different combinations of assignments of the programs is,
[tex]_^{20}C_{4} = \frac{20!}{4!(20-4)!}[/tex]
[tex]_^{20}C_{4} = \frac{20.19.18.17.16!}{4.3.2.1(16)!}[/tex]
[tex]_^{20}C_{4} = \frac{20.19.18.17}{4.3.2.1}[/tex]
[tex]_^{20}C_{4} = \frac{116280}{24}=4845[/tex]
Hope this helps!