Just answer the question

Cust: I want to try that jacket
EM: ok, what size did you need?
Cust: I don't know
EM: what size do you take in a shirt to get it done up?
Cust: I have lots of sizes
EM: ok
Cust: I'm a 36 or 38...
EM: it's not done by bra size it's done by dress size. For example if I'm a 12 around my waist but can only get a 14 to do up over my bust, then that would make me a 12 RC...
Cust: I'm 89 around my hips and 115 around my top... That's centimetres...
EM: I don't know what that would be in high street sizes...
Cust: what do you think I am
EM: I can't tell at the moment...
Cust: let's try a RC
EM: ok, what size?
Cust: RC
EM: 8, 10, 12, 14, 16 or 18?
Cust: oh 14!
EM: ok, so a RC would make it a 16 in the boobs...
Cust: maybe a SC... I have clothes at home where I have a 12 skirt and an 18 jacket...