Answer
The radar will not work.
Work Step by Step
Using known equations in the chapter, we can find the equation for the velocity that the radar can detect is:
$v = \frac{c\Delta f}{2f} = \frac{(10.8\times10^8 \ km/h)(50\ Hz)}{2\times 5\times10^9 \ Hz}= 5.4 \ km/h$
This is greater than the minimum speed allowed, so the radar will not work.
