Number of isomeric products formed by monochlorination of 2-methylbutane in presence of sunlight is ________.

Number of geometrical isomers possible for the given structure is/are _________.

If $$50 \mathrm{~mL}$$ of $$0.5 \mathrm{M}$$ oxalic acid is required to neutralise $$25 \mathrm{~mL}$$ of $$\mathrm{NaOH}$$ solution, the amount of $$\mathrm{NaOH}$$ in $$50 \mathrm{~mL}$$ of given $$\mathrm{NaOH}$$ solution is ______ g.