Problem 2-98 - Linear Kinematics

A helicopter is traveling horizontally, straight toward a cliff. When $700 \;m$ from the cliff, it sends a sonar signal and $3.4\; s$ later receives the reflected signal. Assuming the signal travels at $350\; m/s$, determine the speed of the helicopter.

In order for this problem to have a reasonable solution:

(A)  The signal speed must be greater than that of the helicopter.

(B)  The signal speed must be less than that of the helicopter.