Regular expression for the language of all those strings having even and consecutive b’s in theory of automata

Write the Regular expression for the language of all consecutive even length a’s ?

Accepted Strings: 

These all strings are the part of the language so should be accepted by regular expression;

Example strings = {aa, aab, aabaa, aabbaa, aababaa,………}and all other strings that contains consecutive even a’s.

Rejected Strings:

These all strings are not part of the language so should be rejected by regular expression;

Example strings = {a, b, ab, ba, aba, bba, abba,……………..} and all other strings that does not contains consecutive even a’s in strings.

R.E = aa (a+b)^*ba