The correct answer is d. 840
The problem ask us to compute the permutations of 7 objects in groups of 4.
To compute this, we use the formula:
[tex]P(n,r)=\frac{n!}{(n-r)!}[/tex]Then for P(7,4):
[tex]P(7,4)=\frac{7!}{(7-3)!}=\frac{5040}{3!}=\frac{5040}{6}=840[/tex]Then P(7,3) = 840
