What is the easiest way to solve,” Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates.

May 15       

 May 16      

 May 19June 17      

June 18

July 14     

 July 16

August 14    

 August 15   

  August 17

Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively. Albert: I don’t know when Cheryl’s birthday is, but I know that Bernard doesn’t not know too. Bernard: At first I don’t know when Cheryl’s birthday is, but I know now. Albert: Then I also know when Cheryl’s birthday is.So when is Cheryl’s birthday?”