you are to write a subroutine using the visual emulator which implements bresenham's algorithm. your program will receive two pairs of coordinate locations; these will be in registers 1 through 4, representing variables called x1, y1, x2, and y2. the stack will serve as a storage area where you will place the coordinates of the pixels which must be colored in to complete a line from (x1,y1) to (x2,y2). (this is not standard practice.) the coordinates will each be a pair of words, which we will call xi and yi respectively. you should call your subroutine l6.