Frequency Calculation of a Longitudinal Wave

In a certain experiment, a wave travels through a medium causing it to oscillate back and forth along the direction of the wave propagation. This phenomenon can be described as a longitudinal wave, where areas of compression and rarefaction propagate through the medium. An observer measures the speed of this wave and finds it to be 300 meters per second (m/s). The observer also determines the wavelength of the wave to be 15 meters.

Based on this information, which of the following options best describes the frequency of the wave?