What effect will 20mg Diazepam and 10mg of Citalopram have?

If taken together what affect will 10mg of Citlaopram and 20-30mg of Diazepam have on someone who has never taken Diazepam before? Would it make someone groggy, slurred speech, droopy eys etc? I know it can make you sleepy but if you have to go out, would it be obvious to other people that the person was "on" something or would they just feel quite tired?