Cobalt was used as an internal standard to analyze a sample of titanium with atomic absorption spectroscopy. A mixture was prepared by combining a 4.00 mL Ti solution of unknown concentration with 2.00 mL of a 10.1 ?g/mL solution of Co. The atomic absorbances were measured as 0.124 and 0.205 for Ti and Co, respectively. As a reference, a standard mixture containing 1.38 ?g Co/mL and 1.36 ?g Ti/mL was prepared and measured to have a signal-to-signal ratio of 2.81 Ti: 1.00 Co. Determine the concentration (moles/L) of titanium in the original unknown solution. M of Ti?