Profit before tax per rupee of sale has risen by 10%. Thus, this value will become: 9.94 × 1.1 = 10.93.
Thus, the total cost would be: 89.07 = Fixed expenses + Variable expenses.
Also, fixed expenses have become 10%, hence variable expenses should be 79.07% → a rise of 13.58 on 65.49 = 20.73% increase