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:
| Year | Network | Play-by-play | Color commentator(s) | Sideline reporter(s) |
| --- | --- | --- | --- | --- |
| 1990.0 | ESPN | Mike Patrick | Joe Theismann | Chris Berman |
| 1991.0 | ESPN | Mike Patrick | Joe Theismann | Chris Berman |
| 1992.0 | ESPN | Mike Patrick | Joe Theismann | Chris Berman |
| 1993.0 | ESPN | Mike Patrick | Joe Theismann | Chris Berman |
| 1994.0 | ESPN | Mike Patrick | Joe Theismann | Chris Berman |
| 1995.0 | ABC | Al Michaels | Frank Gifford and Dan Dierdorf | Lynn Swann and Lesley Visser |
| 1996.0 | ABC | Al Michaels | Frank Gifford and Dan Dierdorf | Lynn Swann and Lesley Visser |
| 1997.0 | ABC | Al Michaels | Frank Gifford and Dan Dierdorf | Lynn Swann and Lesley Visser |
| 1998.0 | ABC | Al Michaels | Frank Gifford and Dan Dierdorf | Lynn Swann and Lesley Visser |
| 1999.0 | ABC | Al Michaels | Dan Dierdorf and Boomer Esiason | Lesley Visser and Dan Fouts |
Question:
For how many years combined were Frank Gifford and Dan Dierdorf color commentators?
Answer:
4.0