The school sports room needs to buy 50 volleyballs. There are two shopping malls A and B available. The price of volleyballs in both shopping malls is 28 yuan, but the preferential methods are different, For every 10 volleyballs bought in department store a, 2 volleyballs will be given away for free. For less than 10 volleyballs bought in department store B, each volleyball will be given a discount of 4 yuan. In order to save money, which store should the school buy? Please explain by calculation

The school sports room needs to buy 50 volleyballs. There are two shopping malls A and B available. The price of volleyballs in both shopping malls is 28 yuan, but the preferential methods are different, For every 10 volleyballs bought in department store a, 2 volleyballs will be given away for free. For less than 10 volleyballs bought in department store B, each volleyball will be given a discount of 4 yuan. In order to save money, which store should the school buy? Please explain by calculation

If you go to a shopping mall, the price of 12 balls = 10 balls = 28 × 10 = 280 yuan, 50 = 12 × 4 + 2
So the total price of 50 balls = 280 × 4 + 28 × 2 = 1120 + 56 = 1176 (yuan)
B Market: the actual price of each ball is 28-4 = 24 yuan, a total of 50 balls,
So total price = 24 × 50 = 1200 (yuan) > 1176 (yuan)
Therefore, it is more cost-effective to go to a shopping mall