81/88 × (6 - 1 13/15) × 1 19/21

81/88 × (6 - 1 13/15) × 1 19/2181/88*(6-13/15)*19/2181/88*77/15*18/2127/8*7/5*19/2127/8*1/5*19/39/8*1/5*19171/40 4 11/40 или 4,275