Negative feedback in Amplifiers.

For the ideal Op-Amp circuit of fig. Determine the output voltage V₀

Find the output voltage, V₀ in the following circuit assuming that the Op-Amps are ideal.

Which of the following demodulator(s) can be used for demodulating the signal $$x(t)\;=\;5\left(1+2\;\cos200\mathrm{πt}\right)\cos\;20000\;\mathrm{πt}$$ .