Enrique has determined that investing $600 per month will enable him to accumulate $10,850 in 11 years and that investing $800 per month will enable him to accumulate $18,250 over the same period. Estimate, using linear interpolation, how much he would have to invest each month to accumulate exactly $16,000. It would take $ a month to accumulate $16,000. (Round to the nearest cent as needed.)