a.
i. Equation for your company: Total cost = 5(number of items) + 5 (shipping cost)
ii. Equation for other company: Total cost = 0.5(cost per item)(number of items) + 20 (shipping cost)
b. If the customer in Alaska wants to buy 5 items, she should buy from your company because your total cost for 5 items is $30 ($25 for items + $5 for shipping), while the other company's total cost is $22.50 ($12.50 for items + $20 for shipping).
c. If the customer in Alaska wants to buy 50 items, she should buy from the other company because their total cost for 50 items is $45 ($25 for items + $20 for shipping), while your company's total cost is $255 ($250 for items + $5 for shipping).
d. Solving the system of equations:
5n + 5 = 0.5n + 20
4.5n = 15
n = 15/4.5
n = 3.33
The customer should buy 4 items (as you cannot buy a fraction of an item) from your company to have a lower total cost.
e. The solution for part D means that the customer should buy 4 items from your company to have the lowest total cost for her purchase, as buying from the other company would result in a higher overall cost even though their cost per item is lower.