Do we write 'mum' (which means mother) in capital?

eg. Can i help you with cooking, mum? 

immediate answers by experts please!

Hello,

I must say dear student that there are no set guidelines on whether 'mum' should be written in capital letters or not. However, it is for sure that 'mum' is another version of the relation 'mother'. Thus, even when we address one's own mother, it can be written as 'mum' and capital letters needn't be used. Thus, the sentence you asked is very correctly written as “Can I help you with cooking, mum?” Hope your doubt is cleared.