A tuning fork of known frequency 256Hz makes 5beats per second with the vibrating string of a piano. The beat frequency decreases to 2beats per second when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was
(a) (256 + 2)Hz
(b) (256 – 2)Hz
(c) (256 – 5)Hz
(d) (256 + 5)Hz.
