(Analyzing coverage ratios) The income statements for Home Depot, Inc. (HD), spanning the period 2014-2016 (just before the housing crash, so these are representative years) are found here:

$ thousands 2016 2015 2014 Net operating income (EBIT) $11,774,000 $10,469,000 $9,166,000 Interest expense $(919,000) $(830,000) $(711,000) Earnings before taxes $10,855,000 $9,639,000 $8,455,000 Income taxes $(4,012,000) $(3,631,000) $(3,082,000) Net income $6,843,000 $6,008,000 $5,373,000

a. Calculate the times interest earned ratio for each of the years for which you have data.

b. What is your assessment of how the firm's ability to service its debt obligations has changed over this period?