Solution:
Let x = the order size of each time
1. Calculate N(x) , the number of orders that the dealer will place in a year
N(x) = 900 / x
2. Calculate C(x) , the storage cost in the year
C(x) = [tex]\frac{x}{2}[/tex] - 1000 = 500x Dollars
3. Calculate R(x), the reorder cost of each time
R(x) = 9000x + 1000 Dollars