worker ?lift ?a ? 20.0 - kg ?bucket ?of ?concrete ?from ?the ?ground ?up ?to ?the ?top ?of ?a ? 20.0 - ?M ?tall ?building ?the ?bucket ?is ?initially ?at ?rest ?but ?is ?traveling ?a ? 4.0 ?m / s ?when ?it ?reaches ?the ?top ?of ?the ?building ?what ?is ?the ?minimum ?amount ?of ?work ?that ?the ?worker ?did ?in ?lifting ?the ?bucket