Davi goes to a warehouse that sells a bottle of orange juice for $\mathrm{R} \$ 2.80$ and a box with six of these bottles for $\mathrm{R} \$ 15.00$. He needs to buy 22 bottles for his birthday. How much will he spend, at a minimum?
If Davi buys six bottles individually, he will spend $6 \times 2.80 = 16.80$ reais, which is a higher amount than the price of a box of six. Therefore, he should buy the largest possible number of boxes. In this case, since $22 = 3 \times 6 + 4$, he should buy three boxes and four individual bottles, in which case he will spend $3 \times 15 + 4 \times 2.80 = 56.20$ reais, which is the minimum possible.