1. The problem statement, all variables and given/known data The cost of fuel to propel a boat through the water (in dollars per hour) is proportional to the cube of the speed v. A certain ferry boat uses $100 worth of fuel per hour when cruising at 10 miles per hour. Apart from fuel, the cost of running this ferry (labor, maintenance, and so on) is $3125 per hour. (a) Find the proportionality constant for the cost of the fuel per hour. (b) Express the cost per mile in terms of v only. (c) At what speed should the boat travel so as to minimize the cost per mile traveled? 2. Relevant equations 3. The attempt at a solution a) C=kv^3 100=k1000 k=.1 b)C(v)=.1kv^3 + 3125 This is where i get stuck because apparently this is wrong?