The second question. Between the origin and 30: 30 divided by 5 multiplied by 4=24. Beyond it: that is, 30: 30 divided by 3 times the right side of 4=40.
The third question. If mk/7 is an integer (k= 1, 2, 3, 4, 5, 6), then mk can be divisible by 7. For example, M =-3.5, K = 2, 4, 6-because there are three feasible k's, it does not meet the situation of only two points. Let's take k = 3,6, then m=-7/3. Because there are two complete points, M.