In a shallow grain storage bin, grain with an internal angle of friction $\phi = 26.0^\circ$ exerts lateral pressure on a retaining wall. According to Rankine's earth pressure theory, the ratio of passive lateral earth pressure coefficient ($k_p = \frac{1 + \sin\phi}{1 - \sin\phi}$) to the active lateral earth pressure coefficient ($k_a = \frac{1 - \sin\phi}{1 + \sin\phi}$) is ________ (round off to two decimal places).