Chapter 4.3, Problem 86E

Fuel Economy Your used Chevy’s gas mileage (in miles per gallon) is given as a function $M\left(x\right)$ ofspeed x in miles per hour, where

$M\left(x\right)=\frac{4,000}{x+3,025x^{-1}}.$

Calculate $M\text{'}\left(x\right)$ nshence determine the sign of each of the following; $M\text{'}\left(40\right),M\text{'}\left(55\right),$. and $M\text{'}\left(60\right)$

Interpret your results.