Required ratio = (number of units manufactured in the year 2006 - number of units sold in the year 2006)/ (number of units manufactured in the year 2007 - number of units sold in the year 2007)
Required ratio = (5.5 - 5) / (5 - 3) = 0.5 / 2 = 1 / 4 = 1 : 4
