Help me answer this question please !

If the speed of an electromagnetic wave is 100,000 cm/s and its wavelength is 100 cm, what is its frequency? a) 100,000 cycles per second (hz) b) 1 × 10-3 cycles per second (hz) c) 10,000,000 cycles per second (hz) d) 1,000 cycles per second (hz)

Ineed with number 6 , explain how to get 1978

Sara made $253 for 11 hours of work. at the same rate how much would he make for 7 hours of work?