calculate the wavelength in the visible spectrum (3500-7000)angstrom which coincide with the wavelength 6000 angstrom in 5th order?

As learnt

The energy (E) of a quantum of radiation -

Where h is plank’s constant and  is frequency

-

 AND
 

Speed of electromagnetic radiation -

where frequency is (,pronounced as nu), wavelength is (λ) and velocity of light is(c)

-

 We know, 

E= energy of a quantum of radiation

h=plank's constant

 frequency of radiation

and 

Now, 

Put in 2