$2.$ Which of the following is not a within$-$table text calculation?

a$.$ Combining two text fields, such as combining a customer$$s first name John, and last name Doe, resulting in John Doe.

b$.$ Replacing a number of characters in a text field; such as replacing $$str$$ with $$street$$ in an address field.

c$.$ Extracting a substring for a text field. For example, extracting the area code $302$ from telephone number $302-200-5731.$

d$.$ Counting the number of different cells in a text field. For example, counting the different values in the Country field.