please do with no excel, thanks

A tire store orders its stock for a popular winter tire once every year. The cost of a tire for the store is $120. The store sells a tire for $140 at the regular price. The regular demand per year is 1,000 tires, which is normally distributed with a standard deviation of 70 tires. Customers do not prefer to buy from an older stock; hence the store does not keep the tires for the next year. The store can sell the excess stock at a reduced price of $80 per tire. How many tires the store should order each year