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.

a$.$ Compute the average useful life of Deere's depreciable assets at year$-$end $2015.$

Round answer to one decimal place.

$$ years

b$.$ Estimate the percent used up of Deere's depreciable assets at year$-$end $2015.$

Round answer to one decimal place $($ex: $0\mathrm{.}2345=23\mathrm{.}5\%)$

$\%$