The average cost represents the slope of the line of the graph. Increasing the slope of the graph increases the steepness of the line. Therefore, increasing the average cost of gas from $1.50 to $2.20 will increases the steepness of the line. (i.e. the line becomes closer to the vertical line).
We have the area of the base of a triangular prism= a*b the volume of triangular prism =a*b*c( where c is the height) so that 210=a*b*14 ==> 210= base area*14==> base area= 210/14
