Find the step response of a system with the stated equation of motion:

a. \(2 \ddot{x}+10 \dot{x}+12.5 x=10 u_{s}(t)\)

b. \(2 \ddot{x}+10 \dot{x}+8 x=10 u_{s}(t)\)

c. \(2 \ddot{x}+10 \dot{x}+18 x=10 u_{s}(t)\)