Respuesta :
Just use the Fundamental Equation of Periodic Waves:
[tex]v=\lambda f \\ \lambda= \frac{3\times 10^8}{900\times 10^3} \\ \lambda = \boxed {\frac{10^3}{3}~m}[/tex]
[tex]v=\lambda f \\ \lambda= \frac{3\times 10^8}{900\times 10^3} \\ \lambda = \boxed {\frac{10^3}{3}~m}[/tex]