per share
( c ) Book value per share of common stock $
per share
( d ) Payout ratio of common stock
%
( e ) Return on common stock equity
%
4 ) Sisco Co . purchased a patent from Thornton Co . for $ 620,000 on July 1 , 2012 . Expenditures of $ 119,000 for successful litigation in defense of the patent were paid on July 1 , 2015 . Sisco estimates that the useful life of the patent will be 20 years from the date of acquisition .