How is $5000$ represented with $3$ significant figures?

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.

Perform the following calculations for the given exponential numbers:
$(i)$ $(6.7 \times 10^4) \times (8.4 \times 10^7)$
$(ii)$ $\frac{(3.4 \times 10^{-3})}{(6.5 \times 10^{-7})}$

$4 \ L \ atm$ is equal to (in $cal$)

$2 \times 10^{8}$ atoms of carbon are arranged side by side. Calculate the radius of a carbon atom if the length of this arrangement is $2.4 \, cm$.

$A$ jug contains $2 \ L$ of milk. Calculate the volume of the milk in $m^{3}$.