Which smaller units of $kg$ are used to measure the mass of chemicals with very low mass?

The significant figures in $3400$ are

Evaluate the following exponential numbers:
$(i)$ Add $8.56 \times 10^{6}$ and $10.64 \times 10^{5}$.
$(ii)$ Subtract $5.80 \times 10^{-4}$ from $3.33 \times 10^{-3}$.

Select the $INCORRECT$ statement/s from the following:
$(a)$ $22$ books have infinite significant figures
$(b)$ In the answer of calculation $2.5 \times 1.25$,the result has four significant figures.
$(c)$ Zeros preceding the first non-zero digit are significant.
$(d)$ In the answer of calculation $12.11 + 18.0 + 1.012$,the result has three significant figures.

The number of significant figures in $0.00340$ is $......$

What is the temperature of $343 \ K$ in $^\circ F$ (in $^\circ F$)?