The answer is a 20 or 140 u choose because u subtract or add these numbers and sorry I can’t speak sri lanka or Indian but I know how to read them
Explanation:
(a) Frequency of radar energy, 
The relation between frequency and wavelength is given by :




or

(b) If wavelength, 




or
f = 1.2 GHz
Hence, this is the required solution.
Density = mass/volume, so density=5.28g/2cm
All of them apply because they all are doing some thing to move
1 Bc I just did it and got it right