ex 8 a) {0\3,3\3,6\3}
b){3\3,3\6}
c)M
ex11
a){1,2,3,4,5,6,7,9,11,12}
b){2,4,6}
c){}
d){2,4,6,12}
e){1,3}
f){8,10}
