Algebra-1

A car rental company charges a flat fee of $50 plus 0.20 per mile driven. If the total cost for a customer who drove 150 miles is represented by the point  on a graph, and the total cost for a customer who drove 300 miles is represented by the point  , find the slope of the line passing through these points. The slope represents the rate of change of the total cost with respect to the number of miles driven. Express your answer as a decimal. The slope is _______.