3. A filter is needed to recover x2(n) from the signal, x(n) = xi(n) + X2(n) + X3(n), where x1(n) = sin(.4n), x2(n) = sin(1.5n), and x3(n) = cos(2.6n). (a) What kind of filter is required, LP,BP,HP, or BR ? (b) Specify the allowable range for the filter's cut-off frequency or frequencies in radians, and find the corresponding cut-off sample or samples, k, etc, for H(k) in terms of the cut-off frequency or frequencies. (c) Find a closed form for the impulse response h(n) using the inverse DFT, and the cut-off sample or samples. (d) Find a real expression for h(n) from part (c)