(Round off to the NearestInteger)
[Use:Atomicmasses:$Na:23.0\,u \mathrm{O}: 16.0 \,\mathrm{u} \quad \mathrm{H}: 1.0 \,\mathrm{u}$, Density of $\mathrm{H}_{2} \mathrm{O}: 1.0 \,\mathrm{~g} \,\mathrm{~cm}^{-3}$ ]
mass of solution $=(1.2 \times 1000)\, \mathrm{g}$
$=1200\, \mathrm{gm}$
Neglecting volume of $\mathrm{NaOH}$
Mass of water $=1000\, \mathrm{gm}$
$\Rightarrow$ Mass of $\mathrm{NaOH}=(1200-1000)\, \mathrm{gm}$
$=200\, \mathrm{gm}$
$\Rightarrow$ Moles of $\mathrm{NaOH}=\frac{200\, \mathrm{~g}}{50\, \mathrm{~g} / \mathrm{mol}}=5\, \mathrm{~mol}$
$\Rightarrow$ molality $=\frac{5 \,\mathrm{~mol}}{1\, \mathrm{~kg}}=5\, \mathrm{~m}$
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Product $(A)$ is