Table:
|  | 2019 | 2018 | 2017 |
| --- | --- | --- | --- |
| Outstanding | 4.2 | 3.6 | 4.1 |
| Vested and expected to vest | 5.0 | 3.6 | 4.1 |
| Exercisable | 2.1 | 2.4 | 2.8 |
Paragraphs:
Stock options weighted average remaining contractual terms (in years) information at December 31, for the years 2019, 2018, and 2017 is as follows:
As of December 31, 2019, total unrecognized expense related to non-vested restricted stock unit awards and stock options was $45 million, and is expected to be recognized over a weighted average period of 1.8 years.
Question:
In which years is information on Stock options weighted average remaining contractual terms provided?
Answer: 2019, 2018, 2017