As per the question, the number assigned to P is mentioned as 4. The difference between the numbers assigned to P and T is provided as 5. So the number assigned to T must be either 9 (if T is greater than P) or -1 (if T is smaller than P), however, -1 is not a valid assignment as the substituted integers are only between 1 and 9. Therefore, T must be assigned the number 9.

Furthermore, it is mentioned that the difference between N and T is 3. This implies that N should be either 12 or 6. However, since the substituted integers are between 1 to 9, N cannot be 12. Thus, the integer assigned to N should be 6 and not 4 as mentioned in the correct answer.

Alert - correct answer should be 6.