Acertain radio wave has a frequency of 2.0 x10^6 hz

i know that you are supposed to divide by 3.0 x 10^8 but where does that number come from?

Radio wave frequency is given as

here we know that wavelength and frequency si related to each other by equation

now here we need to divide speed of wave by its frequency in order to find its wavelength

So here we know this is radio wave which is a part of electromagnetic wave

So here we need to use the speed of electromagnetic waves

So here the speed of electromagnetic waves is same as speed of light so we can use it as

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.