Identify the correct equation for the equilibrium constant $K$ for the formation of iron$($III$)$ thiocyanate.

$F{e}^{3+}(aq)+SC{N}^{-}(aq)FeSC{N}^{2+}(aq)$

Select one:

$K=\frac{[FeSC{N}^{2+}]}{[F{e}^{3+}][SC{N}^{-}]}$

$K=\frac{[F{e}^{3+}][SC{N}^{-}]}{[FeSC{N}^{2+}]}$

$K=\frac{[FeSC{N}^{2+}{]}^2}{[F{e}^{3+}{]}^3[SC{N}^{-}]}$

$K=[F{e}^{3+}][SC{N}^{-}]$