已知a={1,3,5,7},b={1,4,7},c={2,5,7,8}.anb={1,3,5,7,}n{11,44,7,}={1,7}；
anb={1,3,5,7,}u{111,444,7}={1,3,4,5,7}.根据此规定,可求的(a u c)n b={?}