Four distinct integers a, b, c, and d are chosen from the set \{1,2,3,4,5,6,7,8,9,10\}. What is the greatest possible value of a c+b d-a d-b c?
Four distinct integers a, b, c, and d are chosen from the set \{1,2,3,4,5,6,7,8,9,10\}. What is the greatest possible value of a c+b d-a d-b c?