Need of Correct Answers

The Author has a sketchy Model with incomplete variable data (no determinate level of discretion), which he developed adhoc. Readout says Truck Cargo-ton miles will begin to decrease if Fuel exceeds $2.61/gallon, a Price level which can be reached if Oil Price reaches $63.45/barrel. The Author is notorious for poor Math skills, and he sketched out the Model on Spiral paper. Please redirect to competent Studies. lgl