Round of Drinks Joke

A blonde, a brunette and a redhead went into a bar and asked the bartender for some drinks:

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 13."

Bartender: "What's a 13?"

Blonde: "7 and 7."