[填空题]
A guitar string produces 4 beats/s when sounded with a 350-Hz tuxnx0oql4hnr/a5 *5 j msp(j6nne h9 3cvm9qmo1ing fork and 9 beats/s when sounded with a 355-Hz tuning fork. What is the vibrational frequency oc91v oe9hmm3q f the string? Explain your reasoning. Hz