Wohlfahrt's Theorem for the Hecke group G5

Let K be a subgroup of the inhomogeneous Hecke group G5 of geometric level r. Then K is congruence if and only if K contains the principal congruence subgroup G(2r). In the case r≢0(mod4), K is congruence if and only if K contains the principal congruence subgroup G(r).