I hate it when I'm asked to do Task A - I'm halfway through Task A when another person comes along and asks me to do Task B.
"Can I finish Task A first, then I settle Task B?"
"No, can you do it now?"
I turn to apologise to the person who requested Task A, he says nevermind, do Task B, and I start on Task B with the person who requested grudgingly and feeling bad that I am unable to fulfil Task A for the other person.
Isn't it basic manners that it's RUDE to INTERRUPT, even if a person is in a task? If a person is busy, WAIT. He/she will do it for you, not now, but later. CAN OR NOT?