String 1 in FIGURE P16.47 has linear density 2.0 g/m and string 2 has linear density 4.0

Question:

String 1 in FIGURE P16.47 has linear density 2.0 g/m and string 2 has linear density 4.0 g/m.
A student sends pulses in both directions by quickly pulling up on the knot, then releasing it.
What should the string lengths L₁and L₂be if the pulses are to reach the ends of the strings simultaneously?

4.0 m String 2 String 1 Knot L FIGURE P16.47