SELECT count(*) FROM driver WHERE home_city  =  'Hartford' OR age  <  40
How many drivers are from Hartford city or younger than 40?
[Schema (values) (types)]: | school_bus |  driver : driver_id (text) , name (number) , party (text) , home_city (text) , age (text) | school : school_id (text) , grade (number) , school (text) , location (text) , type (text) | school_bus : school_id (text) , driver_id (number) , years_working (text) , if_full_time (text);