Scattergraph Method, High$-$Low Method

Deepa Dalal opened a free$-$standing radiology clinic. She had anticipated that the costs for the radiological tests would be primarily fixed, but she found that costs increased with the number o tests performed. Costs for this service over the past nine months are as follows:

$\backslash$table$[[$Month$,$Radiology Tests,Total Cost$],[$January$,2,800,$$$133,500$