Albert and Bernard just become 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 19 |
|---|---|---|
| June 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 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?