Please write answer neatly... 4. Use MATLAB - Consider three sinusoidal signals with the following amplitudes and phases: xi(t) = 5 cos( 211 - 500t) xz(t) = 5 cos( 211 1200t +0.251) X3(t) = 5 cos( 217 1800t + 0.51) a. Create a MATLAB program to sample each sinusoid and generate a sum of three sinusoids, that is, x(n) = x1(n) + x2(n) + x3(n), using a sampling rate of 10,000 Hz. Plot x(n) over the range of 0 to 4 milisecond. b. Use MATLAB function fft() to compute DFT coefficients, then plot and examine the spectrum of the original signal