State Bank of India , the country's largest lender by assets, more than doubled its fourth-quarter profit as its bad-loan ratio narrowed. Net income climbed to 28.1 billion rupees , or 3.55 rupees a share, in the three months ended March 31 from 12.6 billion rupees, or 1.64 rupees, a year earlier, the Mumbai-based lender said in an exchange filing on Friday.