decode two values using oracle decode

decode two values using oracle decode

select status_a,status_b from test
how to decode status_a,status_b below values using oracle decode function .
if status_a='Y' or status_b='Y' then 'Y'
if status_a='Y' or status_b='N' then 'N'
if status_a='N' or status_b='Y' then 'N'
if status_a='N' or status_b='N' then 'N'
Regards,
Chaituhara