The oxygen consumption (in milliliter per pound per minute) for a person walking at x mph is approximated by the function f(x)=\frac{5}{3} x^{2}+\frac{5}{3} x+10 \quad(0 \leq x \leq 9)whereas the oxygen consumption for a runner at x mph is approximated by the function g(x)=11 x+10 \quad(4 \leq x \leq 9) b. At what speed is the oxygen consumption the same for a walker as it is for a runner? What is the level of oxygen consumption at that speed?