一道英文数学题!微积分的!
atroughis6mlonganditsendshaveshapepfisoscelestrianglesthatare1maccrossatthetopandhaveaheightof50cm.ifthetroughisbeingfilledwithwateratarateof1.2m^3/min,howfastisthewaterlevelrisingwhenwateris20cmdeep?