If MANIC - 2 then D is the fourth letter because MANIA - 1 and PANDA - 2; the A, N, and A in MANIA must account for the one since if it is the M or the I then the A, N, and A in PANDA would be excluded and you could not have PANDA - 2. Therefore either the P or D in PANDA must be correct. MANIC - 2 and PANIC - 2 would eliminate the P. If MANIC - 0 then A is the last letter because MANIA - 1, the only difference being the A.