Use modal analysis to derive an expression for the transfer receptance a21 of the system shown in figure 1 with k1=3000 N/m, k2=k3=2000 N/m, k4-1000 N/m and m1=m2=m3=1 kg. Determine the frequencies at which resonance and anti-resonance occur. www.m-www.mz wwww k f2 k U1 k3 f3 ka Figure 1