7. In order to clear the inventory, Crab Boss decides to offer a discount promotion on hamburgers. If he offers a 90% of the original price, he can still make a profit of 320 berries per hamburger; if he offers a 70% of the original price, he will incur a loss of 160 berries per hamburger. Then, the purchase price of each hamburger is $\qquad$ berries.
$1840$