Three different type of glasses are used to make a large glass slab. The thermal conductivity of glass slabs are $k_1,k_2$ and $k_3.$ The width of each glass slab is $\omega$ and cross-sectional area is $A$. The glass slabs are kept in a pattern as shown in the figure. The upper surface of glass slab is maintained at temperature $T_1$ and lower surface at  $T_2$ . It is given that $k_1=1.10W/mK, k_2=2.82W/mK, k_3=2.08W/mK, w=10cm,A=1.3m^2,T_1={100}^{0}C,T_2=0^{0}C.$ Find equivalent thermal conductivity of large glass slab in W/mK.