Answer
$$2.058\;m$$
Work Step by Step
Let the length of the spermaceti sac is $L$
The sound from the Distal sac first goes to Frontal sac and then it again reflects back to Frontal sac through the spermaceti sac.
So, the total distance covered by the sound is $2L$
Therefore, the time required to cover $2L$ distance is
$t = 2L/v$
From the strip-chart, we obtain that the time between clicks is $t=3\;ms$. Velocity of sound through the spermaceti sac is $v =1372\;m/s$.
Thus, we find
$L=\frac{vt}{2}$
Substituting the known values, we obtain
$L=\frac{1372\times3\times10^{-3}}{2}\;m$
or, $L=2.058\;m$
Therefore, the length of the spermaceti sac is $2.058\;m$
