The case where c2/ci = a/b is useful for the construction of examples. However, the numbers ci and c2 arise from /, which is given in advance, and they are usually such that c2/c is not rational. To solve this general case, we approximate by solutions of cases where c2/ci is rational. If the particle takes steps of size 1 to the right with probability p and steps of size ri = ai/bi>c2/c to the left with probability g, then clearly the probability Ui of absorption below cz/ci is larger than the true value. Similarly, if 1