My try:

\(w\,(t)=p\,t\)

\(w\,(t)=v\,i\,t

w\,(t)=v\,\left(\frac{q}{t}\right)\,t

w\,(t)=v\,\left(\frac{q}{\cancel{t}}\right)\,\cancel{t}

w\,(t)=v\,q

w\,(t)=\int_{0}^{0.05} \left(120e^{-2t}\right)\,\left(\dfrac {-30e^{-4t}}{1000}\right)\,dt \)(division by 1000 for converting mC to C)

\(w\,(t)=-0.15 J \)

I feel something wrong with my solution. What is that?