Pierre, a Sole Trader, Is in Business Selling Ovens to Restaurants

Pierre, a sole trader, is in business selling ovens to restaurants and hotels.During the financial year ended 31 December 20X4, his gross profit margin was 32%, an improvement over the previous year's margin of 30.5%.Pierre has come up with two possible reasons for the improvement: A.'I put my prices up by 5% when one of my main competitors went out of business in July, and fortunately, the price increase doesn't seem to have had an adverse effect on trading volumes'.
B. 'The local authority's been charging me far too much in business rates ever since I moved to these premises.At the start of the year I applied for a rate rebate, and in April I received a really substantial refund'.
Which of these reasons has contributed to the improvement in gross profit margin?

A) Reason B only
B) Both A and B
C) Neither A nor B
D) Reason A only