Blonde, Brunette, Redhead ordering drinks

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"