Answer:
6 four-packs.
Step-by-step explanation:
My reasoning for 6 four-packs is that, the shopper needs 24, right? And if that shopper buys 6 four-packs it'll be cheaper than the larger package. The 6 four-packs come to a cost of $20.04. But the 4 six-packs will come out as $21.12. The shopper will be able to save $1.08 :)