Commonwealth Bank's home loan and credit card arrears picked up a little in the March quarter and its net interest margin was "marginally lower". Otherwise, the bank reported a third quarter result that was in line with its first half. CBA reported an unaudited cash profit of A$2.2 billion for the three months to March - up from $1.9 billion in the March quarter last year.It did not provide exact NIM or arrears figures. The bank said it had "positive jaws", which meant that income growth was greater than expense growth.Low interest rates supported strong new mortgage lending activity but was offset by a higher level of loan repayments.According to Australian Prudential Regulation Authority data, CBA's mortgage portfolio (including its subsidiary Bankwest) grew by 1.3 per cent in the March quarter, compared with system growth of 1.4 per cent over the same period.Impaired assets were unchanged at $3.9 billion. The impairment expense for the quarter was $204 million.CBA said business lending growth was "subdued". According to APRA, the bank's business lending book increased by 2.2 per cent in the March quarter, compared with system growth of 1.8 per cent.