Stegman,Ltd AThe Above Data Provide Three Possible Activity Measures That Could

Stegman,Ltd.,provides nationwide passenger train service on 21,000 miles of routes.Selected operating data for fiscal 2014 are shown below.
$$\begin{array}{|l|c|c|c|c|}\hline & \textbf {Fuel Expense} & \textbf {Passengers} & \textbf {Passenger} & \textbf {Train Miles} \\\hline \underline{\textbf {Month}} & \underline{\textbf {000s}} & \underline{\textbf {000s}} & \underline{\textbf {Miles 000 s}} & \underline{\textbf {000s}} \\\hline \text {October 2013} & \$20,075 & 2,145 & 450,857 & 3,098 \\\hline \text {November 2013} & \$22,037 & 2,154 & 451,448 & 3,091 \\\hline \text {December 2013} & \$22,435 & 2,180 & 373,533 & 3,141 \\\hline \text {January 2014} & \$23,613 & 2,151 & 377,438 & 3,178 \\\hline \text {February 2014} & \$21,931 & 2,136 & 461,088 & 2,825 \\\hline \text {March 2014} & \$26,204 & 2,174 & 458,762 & 3,175 \\\hline \text {April 2014} & \$24,698 & 2,207 & 470,311 & 3,096 \\\hline \text {May 2014} & \$24,832 & 2,296 & 492,429 & 3,197 \\\hline \text {June 2014} & \$23,239 & 2,291 & 540,655 & 3,076 \\\hline \text {July 2014} & \$24,481 & 2,414 & 578,133 & 3,191 \\\hline \text {August 2014} & \$25,459 & 2,430 & 563,986 & 3,315 \\\hline \text {September 2014} & \$25,021 & 2,148 & 448,263 & 3,066 \\\hline\end{array}$$
a.The above data provide three possible activity measures that could influence fuel expense.Use the high-low method to develop a cost formula for fuel expense for each of the three measures.
b.Do any of the cost formulas you developed in a appear to be a poor choice for estimating future train operations expense? Why?
c.Which formula do you think will make the most accurate predictions? Why?