AM radio station frequency for 75m tower as quarter-wavelength antenna

[SAT2400]

URGENT! Frequency question

Homework Statement

A radio antenna for an AM station is 75m high tower that is equivalent to lamda/4; another lamda/4 corresponds to ground reflection. At what frequency does the station transmit?

Homework Equations

v=f(lamda)
E=cB

The Attempt at a Solution

Actually, I am not sure what equation to use!?

Please help..I think it's a simple question if i know the equation

 

[rl.bhat]

What is the velocity of radio waves?
Use the relevant equation to find f.

 

[SAT2400]

THe answer is 1M Hz..v=f lamda
is not the right equation to use?

 

[rl.bhat]

The formula is correct. In the problem wavelength λ = 2*150m. What is the velocity of radio waves?