A tuning fork of known frequency 256 Hz makes 5 beats per second with the vibrating string of a piano. The beat frequency decreases to 2 beats per second when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was\\
(1) $256 + 2 \mathrm{~Hz}$\\
(2) $256 - 2 \mathrm{~Hz}$\\
(3) $256 - 5 \mathrm{~Hz}$\\
(4) $256 + 5 \mathrm{~Hz}$