C is the code {aadcca, adcacd, cdabaa, dcbdbc}. By using symbol andj or positional permutations find an equivalent code C' with the following features:

(a) Each word of C' starts with a different letter;

(b) The first and last letters of each word of C' are the same;

(c) b occurs twice in one position of the code.

[The code C' is not unique!]