Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Tie no | Home team | Score | Away team | Date |
| --- | --- | --- | --- | --- |
| 1 | Blackpool | 1–0 | Burnley | 6 Jan 1990 |
| 2 | Bristol City | 2–1 | Swindon Town | 6 Jan 1990 |
| 3 | Rochdale | 1–0 | Whitley Bay | 6 Jan 1990 |
| 4 | Watford | 2–0 | Wigan Athletic | 6 Jan 1990 |
| 5 | Reading | 2–1 | Sunderland | 6 Jan 1990 |
| 6 | Leicester City | 1–2 | Barnsley | 6 Jan 1990 |
| 7 | Nottingham Forest | 0–1 | Manchester United | 7 Jan 1990 |
| 8 | Blackburn Rovers | 2–2 | Aston Villa | 6 Jan 1990 |
| Replay | Aston Villa | 3–1 | Blackburn Rovers | 10 Jan 1990 |
| 9 | Wolverhampton Wanderers | 1–2 | Sheffield Wednesday | 6 Jan 1990 |
| 10 | Middlesbrough | 0–0 | Everton | 6 Jan 1990 |
| Replay | Everton | 1–1 | Middlesbrough | 10 Jan 1990 |
| Replay | Everton | 1–0 | Middlesbrough | 17 Jan 1990 |
| 11 | West Bromwich Albion | 2–0 | Wimbledon | 6 Jan 1990 |
| 12 | Sheffield United | 2–0 | Bournemouth | 6 Jan 1990 |
| 13 | Tottenham Hotspur | 1–3 | Southampton | 6 Jan 1990 |
| 14 | Manchester City | 0–0 | Millwall | 6 Jan 1990 |
| Replay | Millwall | 1–1 | Manchester City | 9 Jan 1990 |
| Replay | Millwall | 3–1 | Manchester City | 15 Jan 1990 |
| 15 | Northampton Town | 1–0 | Coventry City | 6 Jan 1990 |
| 16 | Brighton & Hove Albion | 4–1 | Luton Town | 6 Jan 1990 |
| 17 | Plymouth Argyle | 0–1 | Oxford United | 6 Jan 1990 |
| 18 | Hull City | 0–1 | Newcastle United | 6 Jan 1990 |
| 19 | Crystal Palace | 2–1 | Portsmouth | 6 Jan 1990 |
| 20 | Chelsea | 1–1 | Crewe Alexandra | 6 Jan 1990 |
| Replay | Crewe Alexandra | 0–2 | Chelsea | 10 Jan 1990 |
| 21 | Exeter City | 1–1 | Norwich City | 6 Jan 1990 |
| Replay | Norwich City | 2–0 | Exeter City | 10 Jan 1990 |
| 22 | Huddersfield Town | 3–1 | Grimsby Town | 6 Jan 1990 |
| 23 | Cardiff City | 0–0 | Queens Park Rangers | 6 Jan 1990 |
| Replay | Queens Park Rangers | 2–0 | Cardiff City | 10 Jan 1990 |
| 24 | Port Vale | 1–1 | Derby County | 7 Jan 1990 |
| Replay | Derby County | 2–3 | Port Vale | 10 Jan 1990 |
| 25 | Charlton Athletic | 1–1 | Bradford City | 7 Jan 1990 |
| Replay | Bradford City | 0–3 | Charlton Athletic | 10 Jan 1990 |
| 26 | Leeds United | 0–1 | Ipswich Town | 6 Jan 1990 |
| 27 | Torquay United | 1–0 | West Ham United | 6 Jan 1990 |
| 28 | Hereford United | 2–1 | Walsall | 6 Jan 1990 |
| 29 | Stoke City | 0–1 | Arsenal | 6 Jan 1990 |
| 30 | Birmingham City | 1–1 | Oldham Athletic | 6 Jan 1990 |
| Replay | Oldham Athletic | 1–0 | Birmingham City | 10 Jan 1990 |
| 31 | Cambridge United | 0–0 | Darlington | 6 Jan 1990 |
| Replay | Darlington | 1–3 | Cambridge United | 9 Jan 1990 |
| 32 | Swansea City | 0–0 | Liverpool | 6 Jan 1990 |
| Replay | Liverpool | 8–0 | Swansea City | 9 Jan 1990 |
Question:
What is the tie no of the game where exeter city was the home team?
Answer:
21.0