Number of elements in set B, corresponding to m=1 are 9 m=2 are n=3,5,7,9=4 m=3 are n=4,5,7,8,10=5 m=4 are n=5,7,9=3 m=5 are n=6,7,8,9=4 m=6 are n=7=1 m=7 are n=8,9,10=3 m=8 are n=9=1 m=9 are n=10=1 Total number = 9 + 4 + 5 + 3 + 4 + 1 + 3 + 1 + 1 = 31