4. The transfer function of a circuit is of the form H(s)=(( s+4)(2s+1))/( (s+1+j1)(s+1-j1)).

a. Express the transfer function in descending powers of s with the coefficients of the highest power of s unity in both the numerator and denominator.

b. Determine where the poles and zeroes of the transfer function are located.

c. Is this the transfer function of a causal system? Justify your answer.

d. Discuss the stability of the system.