An inference engine is .
a. a strategy for searching the rule base in case-based reasoning.
b. the programming environment of an expert system.
c. a method of organizing expert system knowledge into chunks.
d. a strategy used to search through the rule base in an expert system by forward chaining or backward chaining.

With only a part-time job and the need for a professional wardrobe, rachel quickly maxed out her credit card the summer after graduation. with her first full-time paycheck in august, she vowed to pay $270 each month toward paying down her $8 comma 368 outstanding balance and not to use the card. the card has an annual interest rate of 18 percent. how long will it take rachel to pay for her wardrobe? should she shop for a new card? why or why not?