ANSWER
[tex]1,088,430[/tex]EXPLANATION
We want to find the number of ways that the books can be selected.
To do this, we have to find the combination of 73 and 4. That is:
[tex]^{73}C_4[/tex]Simplifying, we have:
[tex]\begin{gathered} ^{73}C_4=\frac{73!}{(73-4)!4!} \\ \Rightarrow\frac{73!}{69!4!}=\frac{73\cdot72\cdot71\cdot70\cdot69!}{69!\cdot4!} \\ \Rightarrow\frac{73\cdot72\cdot71\cdot70}{4\cdot3\cdot2\cdot1} \\ \Rightarrow1,088,430 \end{gathered}[/tex]That is the number of ways that the books can be selected.
