if zone =< 2 and ticketType = "adult":
          fare += 23
     elif zone =< 2 and ticketType = "child":
          fare += 11.5
     elif zone == 3 and ticketType = "adult":
          fare += 34.5
     elif zone == 3 or 4 and ticketType = "child":
          fare == 23
     elif zone == 4 and ticketType = "adult":
          fare += 46
     elif zone => 4:
          fare == -zone

     return(fare)