The electric field in a region is given by $\overrightarrow E = \left( {{3 \over 5}{E_0}\widehat i + {4 \over 5}{E_0}\widehat j} \right){N \over C}$. The ratio of flux of reported field through the rectangular surface of area 0.2 m² (parallel to y $-$ z plane) to that of the surface of area 0.3 m² (parallel to x $-$ z plane) is a : b, where a = __________ [Here ${\widehat i}$, ${\widehat j}$ and ${\widehat k}$ are unit vectors along x, y and z-axes respectively.]