## Online Course Discussion Forum

### MC II-B HW Questions

Hello!

I'm slightly confused on how to do 7.23 and 7.24. Any help is appreciated. Thanks!

For 7.23 start by figuring out how many elements you have in each of the sets. Clearly $A$ has $5$ elements. How about $B$? (That is, how many subsets does $A$ have?). Now, to have an injection from $A$ to $B$, you need to assign to each element of $A$ a different element of $B$. In how many ways can this be done?

For a hint on 7.24 check out the post below this.

If you need an extra push, let us know.

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