Maths Classes

*Question:-*
_*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.*_

(1)May 15
(2)May 16
(3)May 19
(4)June 17
(5)June 18
(6)July 14
(7) July 16
(8)August 14
(9)August 15 (10)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 does 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?*