Use the information from the following table:

$\backslash$table$[[$Cost Pool,Total Cost,Allocation Base,Units$],["$A$",$$$120,000,$# of purchase orders,$2,000],["$B$",$$$85,000,$# of inspections,$5,000],["$C$",$$$120,000,$# direct labour hours,$24,000],["$D$",$$$75,000,$# machine hours,$15,000]]$

Which of the following activity rates is incorrectly calculated?

a$.$ $$\frac{17}{?}$ inspection

b$.$ $$\frac{5}{?}$ machine hour

c$.$ $$\frac{60}{?}$ purchase order

d$.$ $$\frac{50}{?}$ direct labour hour