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:
|  | Twelve Months Ended December 31, | Twelve Months Ended December 31, | Twelve Months Ended December 31, |
| --- | --- | --- | --- |
|  | 2018 | 2017 | % Change |
| Wages | $1,658 | $1,468 | 12.9% |
| Pension—Defined benefit plans | 48 | 39 | 23.1% |
| Defined contribution plans | 126 | 103 | 22.3% |
| Medical and other benefits | 245 | 216 | 13.4% |
| Payroll taxes | 113 | 105 | 7.6% |
| Total wages and benefits | $2,190 | $1,931 | 13.4% |
Question:
What is the change of pension cost (in millions) for Alaska airline in 2018 comparing to the previous year?
Answer:
23.1%