code groups

*In a certain digital system, the decimal numbers from 000 through 999 are represented in BCD code. An odd -parity bit is also included at the end of each code group. Examine each of the code groups below, and assume that each one has just been transferred from one location to another. Some of the groups contain errors. Assume that no more than two errors have occurred for each group. Determine which of the code groups have a single error and which of them definitely have a double error. ( Hint: Remember that this is a BCD code.)
(a) 1001010110000
(b) 0100011101100
(c) 0111110000011
(d) 1000011000101
parity bit