A fixed-free rectangular steel beam ( (left.ho=7850 mathrm{~kg} / mathrm{m}^{3}, E=210 times 10^{9} mathrm{~N} / mathrm{m}^{2} ight)) with a length of (1 mathrm{~m}), base of

A fixed-free rectangular steel beam ( \(\left.ho=7850 \mathrm{~kg} / \mathrm{m}^{3}, E=210 \times 10^{9} \mathrm{~N} / \mathrm{m}^{2}\right)\) with a length of \(1 \mathrm{~m}\), base of \(2 \mathrm{~cm}\), and height of \(5 \mathrm{~cm}\) is subject to a single frequency harmonic excitation. List all excitation frequencies that should be avoided to avoid all primary, secondary, and combination resonances involving the three lowest modes.