Table: australian_reps_90_93
Columns: member
party
electorate
state
term_in_office

Question: Name the term in office for liberal and state of sa for ian mclachlan
SQL: SELECT "term_in_office" FROM australian_reps_90_93 WHERE "party" = 'liberal' AND "state" = 'sa' AND "member" = 'ian mclachlan'