Table: fa_cup_match_19
Columns: tie_no
home_team
score
away_team
attendance

Question: What was the attendance when the Southend United was the home team?
SQL: SELECT "attendance" FROM fa_cup_match_19 WHERE "home_team" = 'southend united'

Question: Who was the away team that played Northampton Town at home with a tie number of replay?
SQL: SELECT "away_team" FROM fa_cup_match_19 WHERE "tie_no" = 'replay' AND "home_team" = 'northampton town'