(10) Suppose it to be known that consumption of coal by a certain steamer may be represented by the formula ${\displaystyle y=0.3+0.001v^{3}}$; where ${\displaystyle y}$ is the number of tons of coal burned per hour and ${\displaystyle v}$ is the speed expressed in nautical miles per hour. The cost of wages, interest on capital, and depreciation of that ship are together equal, per hour, to the cost of ${\displaystyle 1}$ ton of coal. What speed will make the total cost of a voyage of ${\displaystyle 1000}$ nautical miles a minimum? And, if coal costs ${\displaystyle 10}$ shillings per ton, what will that minimum cost of the voyage amount to?

(11) Find the maxima and minima of

(12) Find the maxima and minima of