Damp forced vibration help?

Can anyone answer this?

The figure shows the meter used to study the motion yB = bsinωt.

The motion of the mass relative to the frame is recorded on the drum.

If l1= 360 mm, l2= 480 mm, l3= 600 mm, m = 0.9 kg, c = 1.4 Ns/m and

ω = 10 rad/s, Determine the range of the spring constant k over which the magnitude of the recorded relative displacement is less than 1.5b. It is assumed that the ratio ω/ωn must remain greater than unity

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