Answer:
This question is incomplete
Explanation:
This question is incomplete because of the absence of the average velocity at which the supplies are travelling in air. The formula to be used here if the completed question is obtained is
Average velocity (in m/s) = distance (m) ÷ time (s)
Since we are looking for the time, then time should be made the subject of the formula
time (in secs) = distance ÷ average velocity
Hi there!
We can use the following equation:

v = velocity of wave (m/s)
λ = wavelength (μm)
f = frequency (Hz)
We can rearrange the equation to solve for frequency:

Plug in the givens. Make sure to convert μm to m:
1 μm = 0.000001 m

A. All elements. Hope this help I'm sorry if it doesn't!