Two radio antennas $\backslash ($ A $\backslash )$ and $\backslash ($ B $\backslash )$ radiate in phase. Antenna $\backslash ($ B $\backslash )$ is a distance of $100$ m to the right of antenna $\backslash ($ A $\backslash ).$ Consider point $\backslash ($ Q $\backslash )$ along the extension of the line connecting the antennas, a horizontal distance of $30\mathrm{.}0$ m to the right of antenna $\backslash ($ B $\backslash ).$ The frequency, and hence the wavelength, of the emitted waves can be varied.

Part A

What is the longest wavelength for which there will be destructive interference at point $\backslash ($ Q $\backslash )?$

Express your answer in meters.