Margaret had enough gas in her speedboat to get to

Berikut ini adalah pertanyaan dari nyomantirtha5 pada mata pelajaran Fisika untuk jenjang Sekolah Menengah Atas

Margaret had enough gas in her speedboat to get to the marina, a trip upstream that took 4.0 hours. Finding it closed for the season, he spent the next 8.0 hours floating back downstream (out of gas) to his cabin. The whole journey takes 12.0 hours. How long will it take if he buys gas at the marina? Assume that the effect of the wind is negligible.