A video game screen is set up such that the character moves from base to base using the drop-slide formula 3v + 4h = 24, where v is the vertical drop, in millimeters, and h is the horizontal slide, in millimeters. For any given screen, the vertical drops are the same and the horizontal slides are the same for all moves in that screen. The total vertical distance is the sum of all vertical drops and the total horizontal slide is the sum of all horizontal slides. Some screen displays require that the vertical drop must be at least 4 millimeters and the horizontal slide must be at least 1.5 millimeters. Which of the following inequalities represents the set of all possible values for the vertical drop, according to this formula?
A. 0 <= v <= 4
B. v >= 4
C. 4 <= v <= 6
D. 6 <= v <= 18