Answer:
The velocity of electromagnetic waves in vacuum or air is about 300,000,000 m/sec or 3x10^5 km/sec.
frequency = velocity/wavelength = 300,000,000/150 = 2,000,000 Hz = 2 MHz
Letter M stands for prefix mega or 1,000,000
Letter k stands for prefix kilo or 1,000
Letter m stands for prefix milli or 0.001