b$)$ Why can the lower control limit not be a negative number?

A$.$ Since the percent of defective records cannot be a negative number.

B$.$ Since the percent of defective records is always a positive number.

C$.$ Since the upper control limit is positive.

D$.$ Since the upper control limit cannot be a negative number.

c$)$ The industry standard for the upper control limit is $0\mathrm{.}10.$ What does this imply about Birmingham Bank's own standards?

The industry standard is the standard at Birmingham Bank.