A single string is made up of two strings of different densities joined together. Each of the strings is 1.40 meter 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 second for a wave to travel from the beginning to the end of the combined string, estimate what is the tension on the combined string?