Concatenate formula with If and Text function

Hi
Is anyone able to help me with the following please ....

I have a time in cell C10 in hh:mm format, in cell D10 I want to add the text "DFL" in front of the time, remove the ":" and add "HRS." at the end of it.
For example "DFL0715HRS." I have been able to get the following formula to work:
=CONCATENATE("DFL",(TEXT(C10,"hhmm")),"HRS.")


However sometimes it may not be a time, it could also be "Rest Day" in cell C10, if it says "Rest Day" I need it to add the text "DFL" in front as before and then change "Rest Day" to "RDFLEXI."
For example "DFLRDFLEXI." I have been able to get the following formula to work but only if it is "Rest Day", if it is a time such as 07:15 it doesn't work, it shows "DFL07157R0.":
=CONCATENATE("DFL",IF(C10="Rest Day","RDFLEXI.",(TEXT(C10,"hhmm"&"HRS."))))

I think it is trying to continue doing something with the text function and I'm totally confused
Any help would be great, thanks in advance
Nic

Thanks Hemesh that works a treat