From your work on parts (a) and (b), you know that
.. r = 3.50
.. s = 140
The composite index of production cost from 2007 to 2009 is 114.2.
(c) If the production cost in 2007 was RM50, then in 2011 it was
.. RM50 * (2009 index) * (2011 index) = RM50 * 1.142 * 1.200 = RM68.52