A feedback amplifier has a low-frequency open-loop gain of 4000 and three poles at \(f_{P 1}=400 \mathrm{kHz}, f_{P 2}=4 \mathrm{MHz}\), and \(f_{P 3}=40 \mathrm{MHz}\). A dominant pole is to be inserted such that the phase margin is 60 degrees. Assuming the original poles remain fixed, determine the dominant pole frequency.