The following particle interaction is proposed.

\[p + {\pi ^ - } \to {K^ - } + {\pi ^ + }\]

In this interaction, charge is conserved.

State, in terms of baryon and strangeness conservation, whether the interaction is possible.

baryon (1+ 0→0 + 0) not conserved and strangeness (0 + 0→−1+ 0) not conserved;
so interaction not possible;