Marking cases in column A that has atributes from column B

Hej Forum,

I just can't figure out, how to make a formula that will write "combo" or "single" for case numbers who have atributes x and z or just x or just z.

My table consist of case numbers duplicated in column A, and attributes in column B. (including a lot more columns with attributes) sort of like this: Column A (case numbers): a,b,b,b,b,c,c,c,c,d,d and column B (attribute x or z): x,z,z,z,x,x,x,z,z,x

I want to make a column where for the given case number (not row), if it has attribute X and Z, its written combo, and if it has just x or just z "single".

Hope someone can help, thanks!

Attached a sample workbook with before and after. Thanks for the advice.

Thank you, it worked, really clever way of doing it.