Answer
(a) $320Hz$ tuning fork
(b) $317Hz$
(c) $324.5Hz$
Work Step by Step
(a) We know that the frequency of the other tuning fork is lower because it satisfies the second beat frequency condition. The $320Hz$ tuning fork has the lower frequency.
(b) The final frequency of the $320Hz$ tuning fork is given as
$320Hz-3Hz=317Hz$
(c) The frequency of the other tuning fork is given as
$320Hz+4.5Hz=324.5Hz$
