In a meter bridge as shown in the figure, it is given that resistance $Y=12.5 \mathrm{\Omega }$  and that the balance is obtained at a distance $39.5 \mathrm{cm}$ from end $A$ (by jockey $J$). After interchanging the resistances $X$ and $Y$ a new balance point is found at a distance $l_2$ from end $A$. What are the values of $X$ (in $\mathrm{\Omega }$) and $l_2$?