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Minh dang tinh noi luc cau be tong duc hang can bang nhung bi vuong mot cho. Do la he so tai trong cua DC va DW, truong hop cu the nao thi dung 0,9 or 0.65. Truong hop nao thi dung 1.25 or 1.5. Minh thu tinh nhung ket qua khong chenh lech nhieu. vi bieu do bao thi chi can he so lon nhat thoi chu, anh chi nao biet lam on giai thich gium.Cam on nhieu.