how to use case query for this task

Question

intime	outtime
08:45	18:11
08:30	20:15

i have a table ,in that table i have intime,outtime

if datediff(hour,'08:45','20:15') hour difference 4 or 5 means put  /

if hour difference 7 or 8 (between 7 and 8) means X

greater than 11 means  X/