You need to buy a new cell phone now and are trying to minimize your cell phone costs for the next 5 years. A new cell phone costs C dollars and lasts for at most 3 years. The estimated maintenance cost for a phone depends on its age; if a phone is in its ith year of life, the cost will be M_i dollars, i = 1, 2, 3. Assuming cell phones have no salvage value and that you have the option each year of buying a new phone (for C dollars), formulate a network model that will minimize your costs over the next 5 years.