1. (6) Two points in a plane (x-y coordinate system) are specified using the coordinates (x1, y1) and (x2, y2). Write a program that gets the points from the user and

(a) calculates the slope of a line through two (non-vertical) points;

(c) outputs the slope to the screen.

(d) If the user enters two points on a vertical line, the denominator of the slope formula will be zero. Fix the program so that the program wont fail if the points are on a vertical line.

(e) (Optional) Write an equation for the line determined by the two points and output it to the screen.