A man is d owner of a winery who recently passed away. in his will, he left 21 barrels (of which 7 r filled wid wine, 7 half full, nd 7 empty) 2 his 3 sons. however, d wine nd barrels must be split so dat each son has d same no. of full barrels, the same no. of half-full barrels nd d same no. of empty barrels. note dat there r no measuring devices handy. how can d barrels nd wine b evenly divided?