To find the domain, make a set out of all the first coordinates:

{5,5,6,6}

Eliminate all the duplicates

{5,6}

That's the domain.

To find the range, make a set out of all the second coordinates:

{6,7,6,7}

Eliminate all the duplicates

{6,7}

That's the range.

That's all there is to it!

Edwin