What is the $SI$ unit of luminous intensity?

How many significant figures should be present in the answer of the following calculations?
$(i)$ $\frac{0.02856 \times 298.15 \times 0.112}{0.5785}$
$(ii)$ $5 \times 5.364$
$(iii)$ $0.0125 + 0.7864 + 0.0215$

What do you mean by $1 \ kg$?

The sum of three values $12.0$, $19.034$ and $2.0143$ is equal to $X$. The number of significant figures in $X$ is

$1 \, \mu g = ........ \, mg$

Match the following prefixes with their multiples:

Prefixes	Multiples
$i$. micro	$10^6$
$ii$. deca	$10^9$
$iii$. mega	$10^{-6}$
$iv$. giga	$10^{15}$
$v$. femto	$10$