Steven owns a card and gift shop. Recent research shows that the average sale in his store is $$7\mathrm{.}50.$ That is$,$ consumers on average spend $$7\mathrm{.}50$ each time they visit. Steven has initiated a loyalty card program which offers one free greeting card for every $10$ cards that a consumer buys in the hope that can increase his store's average sale to $$8\mathrm{.}50$ per visit. This is an effective tactic to use with what kind of repeat purchase objective?

Question $2$ options:

Purchase amount

Purchase frequency

Purchase timing

Category building