def waveSolution(pixel, wfit0, wfit1, wfit2, wfit3, wfit4, wfit5, c3, c4, **kwargs):
    """
    Calculate the wavelength solution givene parameters of a 
    fourth order polynomial.
	The equation is modified from NSDRP_Software_Design p.35.

	Parameters
	----------
	wfit0-5: float
			 The fitting parameters in NSDRP_Software_Design p.35
	c3     : float
	         The coefficient of the cubic term of the polynomial
	c4     : float
			 The coefficient of the fourth-power term of the polynomial
	pixel  : int/array
			 The pixel number as the input of wavelength solution
    order  : int
             The order number as the input of wavelength

    Returns
    -------
    The wavelength solution: array-like


    """
    order = kwargs.get('order', None)
    
    wave_sol = wfit0 + wfit1*pixel + wfit2*pixel**2 + \
               (wfit3 + wfit4*pixel + wfit5*pixel**2)/order + \
               c3*pixel**3 + c4*pixel**4

    return wave_sol