C(10,4,2) <=9

Method of construction: lex covering

 1  2  3  4
 1  5  6  7
 1  8  9 10
 2  3  5  8
 2  3  6  9
 2  3  7 10
 4  5  6 10
 4  7  8  9
 5  6  8  9