Multifactor productivity $=\frac{\text{O}\text{u}\text{t}\text{p}\text{u}\text{t}}{\text{L}\text{a}\text{b}\text{o}\text{r}\text{I}\text{n}\text{p}\text{u}\text{t}+\text{M}\text{a}\text{t}\text{e}\text{r}\text{i}\text{a}\text{l}\text{I}\text{n}\text{p}\text{u}\text{t}+\text{E}\text{n}\text{e}\text{r}\text{g}\text{y}\text{I}\text{n}\text{p}\text{u}\text{t}+\text{C}\text{a}\text{p}\text{i}\text{t}\text{a}\text{l}\text{I}\text{n}\text{p}\text{u}\text{t}+\text{M}\text{i}\text{s}\text{c}\text{.}\text{I}\text{n}\text{p}\text{u}\text{t}}$

Which of the following poses an external elements measurement problem for a truck driver tracking multifactor productivity over a two$-$month period with a truck the under warranty?

Fluctuating fuel costs

Warranty$-$covered truck maintenance costs

Monthly payments on a $5-$year, fixed$-$rate truck loan

Commercial truck insurance payment if no accidents occur during the two$-$month period

Contractual routing software costs