6. If a merchant sells goods that cost 8 yuan each at 10 yuan each, he can sell 100 pieces per day. Now he is using the method of raising the price and reducing the purchase quantity to increase profits. Given that the price of each item is set to how much, can maximize the daily profit? And find the maximum profit.
6. When the price is set at 14 yuan, the daily profit is maximized, with the maximum profit being 360 yuan.