Use Southwest Airlines 2016 financial statement information, below to answer the following:

1. Calculate Southwest Airlines return on assets (ROA) for the year ending December 31, 2016.
2. Disaggregate Southwest Airlines ROA into profit margin (PM) and asset turnover (AT). Explain what each ratio measures.

($ millions)
Total operating revenues	$20,425
Net income	2,244
Total assets, beginning of year	21,312
Total assets, end of year	23,286
Equity, end of year	8,441