When a spring-mass-damper system is subjected to a harmonic force \(F(t)=20 \cos 3 \pi t \mathrm{~N}\), the resulting displacement is given by \(x(t)=0.0125 \cos (3 \pi t-\pi / 3) \mathrm{m}\). Find the work done

(a) during the first second, and

(b) during the first 4 seconds.