Buying drinks at a bar

A blonde, a brunette and a redhead went into a bar and ordered their drinks from the bartender.

Brunette: "I'll have a B and C."

Bartender:"What is a B and C?".

Brunette: "Bourbon and Coke."

Redhead: "And, I'll have a G and T."

Bartender: "What's a G and T?"

Redhead: "Gin and tonic."

Blonde: "I'll have a 15."

Bartender: "What's a 15?"

Blonde: "7 and 7"