Table:
| ($ in millions) |  |  |  |
| --- | --- | --- | --- |
| For the year ended December 31: | 2019 | 2018 | 2017 |
| Cost | $100 | $82 | $91 |
| Selling, general and administrative | 453 | 361 | 384 |
| Research, development and engineering | 126 | 67 | 59 |
| Pre-tax stock-based compensation cost | 679 | 510 | 534 |
| Income tax benefits | (155) | (116) | (131) |
| Net stock-based compensation cost | $524 | $393 | $403 |
Paragraphs:
The following table presents total stock-based compensation cost included in income from continuing operations.
Total unrecognized compensation cost related to non-vested awards at December 31, 2019 was $1.2 billion and is expected to be recognized over a weighted-average period of approximately 2.5 years.
Capitalized stock-based compensation cost was not material at December 31, 2019, 2018 and 2017.
Question:
What was the increase / (decrease) in the cost from 2018 to 2019?
Answer: 100 - 82 = 18