question: Were M1 , M2 , and M3 employed by a company
query: SELECT count(*) WHERE {
  ?x0 a ns:business.employer .
  M1 ns:people.person.employment_history/ns:business.employment_tenure.company ?x0 .
  M2 ns:people.person.employment_history/ns:business.employment_tenure.company ?x0 .
  M3 ns:people.person.employment_history/ns:business.employment_tenure.company ?x0
  }