Explanation:

- We have six people (P, Q, R, S, T, U) born in May, September, and November on the 9th or 16th.

- P was born after R, but not on the same dates as R, indicating they were born in different months.

- The number of people born before S equals those born after T, so S and T have symmetrical positions.

- Q and U share the same birth month.

- T was born in a month with 30 days, which is September.

- Two people were born between R and T.

From the clues:

- R is born early, maybe on 9th May.

- T on 16th September.

- S is likely born after R and before T or after T, creating symmetry.

By arranging these, R is on 9th May, P on 16th November. The sum of dates, 9 + 16 = 25 and the square root of 25 is 5.

The correct answer is:

- Option 3: 5