A cable will be installed from a farmhouse to a series of telephone poles. Part of the cable will be installed underground, D, with a cost of $220 per foot and part will be installed atop the telephone poles, L, with a cost of $80 per foot. The goal is to determine the value of that will minimize the cost of installation. ong M₁ L X ‡ ‡ ‡ ‡ ‡ ‡ ‡ ‡ M₂ If M₁ = 450 feet and M₂ = 900 feet, determine the distance underground, D, as a function of 2 and the distance along the poles, Las a function of . D L The total cost of installing the cable, C, as a function of 2 is C=C(x) = The derivative is C'(x) Solving C'(x) = 0 will determine the value of that minimizes the cost of installing the cable. feet and the minimum cost is C dollars D