A BJT diff-amp is biased with a current source \(I_{Q}=2 \mathrm{~mA}\), and the circuit parameters are \(R_{C}=10 \mathrm{k} \Omega\) and \(R_{B}=1 \mathrm{k} \Omega\). The transistor parameters are: \(\beta=120, f_{T}=800 \mathrm{MHz}\), and \(C_{\mu}=1 \mathrm{pF}\).

(a) Determine the upper \(3 \mathrm{~dB}\) frequency of the differential-mode gain.

(b) If the current source impedance parameters are \(R_{o}=10 \mathrm{M} \Omega\) and \(C_{o}=1 \mathrm{pF}\), find the frequency of the zero in the common-mode gain.