For part 2 we want to cover every rational. To do so, we list the rationals in some orderly fashion so that each rational is listed infinitely many times, e.g., 0, 1, 0/2, -1, 2, 1/2, 0/3, -1/2,
-2, 3, 2/2, 1/3, 0/4, -1/3, -2/2, -3, 4, 3/2, 2/3, 1/4, 0/5, -1/4, -2/3, -3/2, -4 .... The first number in the list could be covered with an open interval of length e/2, the second e/4, the third
e/8, and so on.