Step 1: Use the integrated rate equation for a zero order reaction.
For a zero order reaction,
\[
[P]_t=[P]_0-kt
\]
where
\[
[P]_0=\text{initial concentration}
\]
and
\[
[P]_t=\text{concentration after time } t
\]
Step 2: Calculate the rate constant.
Given,
\[
[P]_0=0.10\ M
\]
and after \(10\ s\),
\[
[P]_{10}=0.05\ M
\]
Using
\[
[P]_{10}=[P]_0-k(10)
\]
\[
0.05=0.10-10k
\]
\[
10k=0.05
\]
\[
k=0.005\ M\,s^{-1}
\]
Step 3: Calculate the concentration after 15 seconds.
Using
\[
[P]_{15}=0.10-(0.005)(15)
\]
\[
=0.10-0.075
\]
\[
=0.025\ M
\]
Step 4: Final conclusion.
Therefore, the concentration of \(P\) after \(15\ s\) is
\[
\boxed{0.025\ M}
\]
Hence, the correct option is (2).