a.	What proportion of gross accounts receivable does BNSF record as an allowance each year? Interpret the year-over-year change in the ratio.
b.	Calculate the common-size amount for accounts receivable, net, for 2016 and 2015.
c.	Compute the accounts receivable turnover for 2016 and 2015. At December 31, 2014, accounts and other receivables, net were $1,386 million.
d.	Do the accounts receivable turnover you calculated above, seem reasonable for a railway company? Explain.