The correct answer is (a).
The percent increase in profit over the previous period is calculated as follows:
Percent increase = (Profit in current period – Profit in previous period) / Profit in previous period * 100%
For the period 2009-10, the percent increase in profit is:
Percent increase = (620 – 590) / 590 * 100% = 5.13%
For the period 2010-11, the percent increase in profit is:
Percent increase = (656 – 620) / 620 * 100% = 6.15%
For the period 2011-12, the percent increase in profit is:
Percent increase = (690 – 656) / 656 * 100% = 5.07%
For the period 2012-13, the percent increase in profit is:
Percent increase = (726 – 690) / 690 * 100% = 5.61%
Therefore, the period with the maximum percent increase in profit is 2009-10.