The Doppler formula for the frequency detected can be written f = f’ (v - vD) / (v - vS), where f’ is the frequency emitted, v is the speed of sound, vD and vs are suitable components of the detector and source velocities. (vD and vs can be of either sign depending on the direction of the motion relative to the S-D axis.) Suppose the source is traveling at 5 m/s away from the detector, the detector is traveling at 7 m/s toward the source, and there is a 3 m/s wind blowing from the source toward the detector. The values that should be substituted into the Doppler shift equation are (in m/s): a. vD = 10 vs = 2 b. vD = -7 vs = -5 c. vD = -7 vs = 5 d. vD = 4 vs = 2 e. vD = -10 vs = -8