A police radar gun used to measure the speed of cars emits an electromagnetic wave (a radio wave) with a frequency of $24\text{GHz}.$ In an area where the speed limit is $30\text{ m/s},$ what should be the shift in the frequency of the wave after reflecting off traffic that is exactly following the speed limit, driving toward the police officer?

• A. $-2.4\text{kHz}$
• B. $2.4\text{kHz}$
• C. $4.2\text{kHz}$
• D. $-4.2\text{kHz}$
• E. $-4.8\text{KHz}$
• F. $4.8\text{kHz}$