hai can cau lon boc do mot lo hang o cang sai gon.sau 3 gio co them 5 can cau be (co cong suat nho hon)cung lam xong viec.ca 7 can cau lam trong 3 gio nua thi xong.hoi moi can cau lam viec mot minh thi bao lau xong cong viec,biet rang ca 7 can cau cugn lam viec tu dau thi trong 4 gio xong viec