Imagine drawing more sets of vertical lines half way between the existing lines, each successive set being half the height of the previous set. This question is now a tough nut. The question asks about how many lines a horizontal bar would cut as you make it lower and lower, in other words you have to decide how many lines there are at the nth stage. You also have to decide what happens to the heights of the lines as you draw more and more sets and what happens to the number of lines as you draw in more and more sets.