The program should have four variables: first_name, last_name, year_of_birth and username. The program should assign suitable values to first_name, last_name and year_of_birth; in particular, a whole number should be assigned to year_of_birth. The program should work out the username by joining first and last name, with a full stop in between, followed by the year of birth - this should be converted to string using str() before joining. The program should then output the username.