Six persons — C, D, B, O, N, and P — are seated in a row facing north. Each has a different age. The following conditions apply: C sits 3rd from one e...

Six persons — C, D, B, O, N, and P — are seated in a row facing north. Each has a different age. The following conditions apply:

• C sits 3rd from one end.
• The person who is 12 years old sits 2nd to the right of C.
• The number of persons to the right of the 12-year-old is equal to the number of persons to the left of D.
• O sits 2nd to the right of the person who is 6 years old.
• Two persons sit between D and B, and B's age is twice that of D.
• N sits to the right of P.
• The person who is 36 years old sits 3rd to the left of the person who is 15 years old.
• O is 18 years old.

Question: How many persons sit between P and D?