[填空题]
A guitar string produceq2n03beg6zv*a un n*x(ci wt +s 4 b.cc69l5.edt2 yq nql xeats/s when sounded with a 350-Hz tuning fork and 9 beats/s when sounded with a 355-Hz tuning fork. What is thetd5y96e nqc xl c.l.2q vibrational frequency of the string? Explain your reasoning. Hz
