$f = 327, mathrm{Hz}$

$v = 1493, mathrm{m/s}$

$lambda = ?$

Wavelength is given by:

$$
lambda = dfrac{v}{f}
$$

When we put known values into the previous equation we get:

$$
lambda = dfrac{1493, mathrm{m/s}}{327, mathrm{Hz}}
$$

Finally:

$$
boxed{lambda = 4.57, mathrm{m}}
$$

$v = 351, mathrm{m/s}$

$f = 298,mathrm{Hz}$

$lambda = ?$

Wavelength is given by:

$$
lambda = dfrac{v}{f}
$$

When we put known values into the previous equation we get:

$$
lambda = dfrac{351, mathrm{m/s}}{298,mathrm{Hz}}
$$

$$
boxed{lambda = 1.18, mathrm{m}}
$$

$v_{o} = 60, mathrm{km/h} = 16.6, mathrm{m/s}$

$f_{s} = 512, mathrm{Hz}$

$v= 343, mathrm{m/s}$

$f_{o} = ?$

We will be using Doppler effect which gives us the following formula:

$$
f_{o} = f_{s} dfrac{v – v_{o}}{v – v_{s}}
$$

When we put known values into the previous equation we get:

$$
f_{o} = 512, mathrm{Hz} dfrac{343, mathrm{m/s} – 0}{343, mathrm{m/s} – 16.6, mathrm{m/s}}
$$

$$
boxed{f_{o} approx 538, mathrm{Hz}}
$$

$v_{o} = 72, mathrm{km/h} = 20, mathrm{m/s}$

$f_{s} = 657, mathrm{Hz}$

$f_{o} = ?$

We will be using Doppler’s effect which gives us the following formula:

$$
f_{o} = f_{s} dfrac{v – v_{o}}{v – v_{s}}
$$

When we put known values into the previous equation we get:

$$
f_{o} = 657, mathrm{Hz} dfrac{343, mathrm{m/s} – 20, mathrm{m/s}}{343, mathrm{m/s} – 0}
$$

$$
boxed{f_{o} approx 620, mathrm{Hz}}
$$

$f_{beat} = dfrac{20}{5.0} = 4.0 = |f_1 – f_2|$

Thus:

$f_1 – f_2 = 4.0 ===> f_2 = f_1 – 4.0 = 262 – 4.0 = 258 Hz$

or:

$f_1 – f_2 = -4.0 ===> f_2 = f_1 + 4.0 = 262 – 4.0 = 266 Hz$

$$
speed = v = lambda f = (0.672)*(488) = 328 m/s
$$