Please help

1. Consider the negative feedback interconnection: u PS) (a) If possible, give an example of P and C transfer functions such that 1+ PC and 1+ PC are stable, but is not. P (b) If possible, give an example of P and C transfer functions such that 2 C 1+PC and are stable, but 1 + PC 1+PC is not. 1 and 2 1+PC 1+ PC (c) If possible, give an example of P and C transfer functions such that P are stable, but is not. + PC