Estimating Useful Life and Percent Used Up The property and equipment footnote from the Deere & Company Equipment and Operations segment follows. Property and Depreciation A summary of property and equipment at October 31 follows. Useful Lives* Property and Equipment ($ millions) (Years) 2015 2014 Land $114 $120 Buildings and building equipment 23 3,460 3,037 Machinery and equipment 11 5,499 5,089 Dies, patterns, tools, etc 8 1,567 1,552 All other 5 875 889 Construction in progress 345 530 Total at cost 11,860 11,217 Less accumulated depreciation 5,846 5,694 Total $6,014 $5,523 *Weighted averages Total property and equipment additions in 2015, 2014 and 2013 were $666 million, $1,016 million and $1,158 million, and depreciation was $692 million, $696 million and $637 million, respectively. a. Compute the average useful life of Deeres depreciable assets at year-end 2015. Round answer to one decimal place. b. Estimate the percent used up of Deeres depreciable assets at year-end 2015. Round answer to one decimal place (ex: 0.2345 = 23.5%)