When AIB released its surprisingly good results on Friday, Bank of Ireland’s share price responded quickly. Bank of Ireland’s shares rose 2.5 per cent on the day, in anticipation of strong results on Monday. The two banks have much in common. Monday’s results didn’t disappoint. Bank of Ireland grew net interest income by 68 per cent from the same period last year to €1.8 billion. Bank of Ireland’s cost base is fairly fixed. So a big increase in interest income (which, for a bank, is like revenue) translates into a very big increase in profits. Profit before tax grew 190 per…