Topic is Signal and Systems. Please explain step-by step and clear for my best understand.

Consider the following periodic signals x(t) = cos(4x) y(t) = sin(4nt) z(t) = x(y() a) Determine the Fourier series coefficients of x(t). b) Determine the Fourier series coefficients of y(t). c) Use multiplication property to determine the Fourier series coefficients of z(t). d) Determine the Fourier series coefficients of z(t) directly using the analysis equation, and compare with the result you obtained in part-c