A single string is made up of two strings of different densities joined together. Each of the strings is 1.40 m long. The first string has linear density 2.30×10?4 kg/m and the second has linear density 1.80×10?4 kg/m. If it takes 2.20×10?3 s for a wave to travel from the beginning to the end of the combined string, what is the tension on the combined string?