If on a straight line graph we notice that the two sets of coordinates are : (5, 20) and (15, 80) we can say that: (Please note coordinates are (x, y)) O slope of the line is -8 O slope of the line is 6, and this can be a possible supply curve O slope of the line is 6, and this can be a possible demand curve O slope of the line is 8, and this can be a possible supply curve