Hint: Write down the expression for p(1) and p(2), and express p(3) as a function of p(1) and p(2). Then write down the general expression for p(n) for any n as a function of p(n-1) and p(n-2).
A cell is rejected if it has multiple-bit error in its header, when the HEC state machine is the “Correction Mode”. In other words, for a cell not to be discarded, it should have at most 1-bit error in its header. The header is 40 bits-long. Hence, P = probability of a cell is rejected when HEC state machine is in the “Correction Mode” can be computed as follows;