The oxidation number of iron in the compound formed during brown ring test for NO$$_3^-$$ iron is ________.

Molality of 0.8 M H$$_2$$SO$$_4$$ solution (density 1.06 g cm$$^{-3}$$) is ________ $$\times10^{-3}$$ m.

Number of ways of arranging 8 identical books into 4 identical shelves where any number of shelves may remain empty is equal to

Let $$\mathrm{A}$$ be the point of intersection of the lines $$3 x+2 y=14,5 x-y=6$$ and $$\mathrm{B}$$ be the point of intersection of the lines $$4 x+3 y=8,6 x+y=5$$. The distance of the point $$P(5,-2)$$ from the line $$\mathrm{AB}$$ is