The fundamental frequency of a sonometer wire is 180Hz when its vibrating length is 80cm, the tension remaining unchanged. With this setting a tuning fork produces 12 beats per second. The vibrating length of the wire is now reduced to 75cm without altering the tension and no beats are heard. The frequency of the tuning fork is
(a) 204Hz
(b) 192Hz
(c) 168Hz
(d) 180Hz