Let x represent the number of minutes and let y represent the cost of x minutes.
When x = 5, y = 5.91
When x = 10, y = 10.86
Slope, m = (x2 - x1)/(y2 - y1)
Slope = (10.86 - 5.91)/(10 - 5) = 4.95/5
Slope = 0.99
The slope represents the cost per minute of call made
