Presented here are summarized data from the balance sheets and income statements of Wiper, Inc.:

WIPER, INC.
Condensed Balance Sheets
December 31, 2017, 2016, 2015
(in millions)
	2017			2016			2015
Current assets	$	681		$	906		$	753
Other assets		2,415			1,922			1,721
Total assets	$	3,096		$	2,828		$	2,474
Current liabilities	$	566		$	805		$	712
Long-term liabilities		1,521			995			842
Stockholders equity		1,009			1,028			920
Total liabilities and stockholders' equity	$	3,096		$	2,828		$	2,474

WIPER, INC
Selected Income Statement and Other Data
For the year Ended December 31, 2017 and 2016
(in millions)
	2017			2016
Income statement data:
Sales	$	3,052		$	2,915
Operating income		298			312
Interest expense		86			67
Net income		197			192
Other data:
Average number of common shares outstanding		41.5			46.9
Total dividends paid	$	52.0		$	52.5

Required:

a. Calculate return on investment, based on net income and average total assets, for 2017 and 2016

b. Calculate return on equity for 2017 and 2016.

c. Calculate working capital and the current ratio for each of the past three years