Answer
$\bf Yes.$
Work Step by Step
To find out if the manufacturer’s claims are true or not, we need to find the electric field amplitude $E_0$ at $r=42$ m.
We know that the radio wave is an electromagnetic wave, so its intensity is given by
$$I =\dfrac{P}{A}=\dfrac{c\epsilon_0 E_0^2}{2}$$
Solving for $E_0$;
$$E_0=\sqrt{\dfrac{2P}{c\epsilon_0 A}}$$
$$E_0=\sqrt{\dfrac{2P}{c\epsilon_0 (4\pi r^2)}}$$
where $A$ is the area of a sphere since the transmitting unit radiates in all directions.
Plug the known;
$$E_0=\sqrt{\dfrac{2(250\times 10^{-3})}{4(3\times 10^8)(8.85\times 10^{-12}) \pi (42)^2}}=\bf 0.092\;\rm V/m$$
This means that the claims of the manufacturer are true since a few steps before 42 m the field strength was 0.1 V/m.
