Can you help me understand what each of the following solvency ratios say about Centurylink (NYSE: CTL) - need to give perspective of strengths and risks of company based on these ratios. I understand that the trend of each of these is important, but do not quite understand how an investor would look at these to determine if they thought Centurylink was a good or bad buy based on these alone.

2017 2018 2019

Debt to Asset Ratio: 49.89% 51.33% 53.59%

Time Interest Ratio: 1.365 .282 -1.358

Free Cash Flow: $772M $3.857B $3.052B