Please include a thorough and step-by-step explanation for why the answer is e

3. Four vehicles are moving as shown below. A B C D Each has its own driver. Vehicles A, B, and C are moving in the same direction (to the right) but vehicle B is moving faster than vehicles A and C. Vehicle D is not moving. Vehicle B is a police car and its siren is producing a sound of a certain frequency fB as heard by the driver in vehicle B. What is the relationship between fA, fB, fc and fo, the frequencies of the siren heard by drivers of the respective vehicles? a. fD > fA> fB > fc b. fo > fc = fB > fA c. fA > fc > fB > fD d. fo > fB > fc > fA e.) fD > fc > fB > fA