Answer
$L=364 m$
Work Step by Step
Solving the previous equation for $L$ yields $$L= \Delta t(\frac{v_mv}{v_m-v})$$ Substituting in values for speed of sound in air (v=343m/s) and speed of sound in steel (v=5941m/s) yields $$L= \Delta t(\frac{v_mv}{v_m-v})=L= (1.00s)(\frac{(343m/s)(5941m/s)}{5941m/s-343m/s})=364m$$
