Unable to generate random number F#

I am working on a small project and am trying to learn F# the functional way ,for some strange reason I am unable to generate a random number and as such unable to get a random date. here is my F# code

let IfancyHerList = [("Sara",1); ("Saima",2); ("Zoe",3);("Scarlett",4);
("Jennifer",5);("Sandra Bullock",6)]

let MyGirlFriend  = List.pick (fun funToNight  ->
                     let n = rand.Next(10)
                     match funToNight with                    
                     | (value,n ) -> Some value
                     |_ -> None) IfancyHerList
printfn "Your date for tonight is %s lucky fella" MyGirlFriend

The let n = rand.Next(10) does generate a random number but not in match block

any suggestion would be most welcome

thanks