The diameter of a radio source on the sky is 0.5. Its average intensity in a certain bandwidth of 500 kHz is 10^-20 W m^-2 Hz^-1 sterad^-1.
a) Calculate the average flux density of the source in this bandwidth.
b) Calculate the total flux density of the source in this bandwidth.
c) Calculate the brightness temperature of the source at 20 cm wavelength.