The power spectral density of a wide-sense stationary random process is given by 

S_X (f) = 10δ(f) + 25sinc²(5f) + 5δ (f - 10) + 5δ (f + 10)

(a) Sketch and fully dimension this power spectral density function.
(b) Find the power in the dc component of the random process.
(c) Find the total power.
(d) Given that the area under the main lobe of the sinc-squared function is approximately 0.9 of the total area, which is unity if it has unity amplitude, find the fraction of the total power contained in this process for frequencies between 0 and 0.2 Hz.