State the number of significant figures in the following : (a) 0.007 m^2 (b) 2.64 * 10^{24} kg (c) 0.2370 g cm^{-3} (d) 6.320 J (e) 6.032 N m^{-2} (f) 0.0006032 m^2

I found an answer from byjus.com
Rounding Off - Definition, Rules, Examples
... length measured, etc are estimated by rounding off the actual number to the ... Rounding off numbers is done to preserve the significant figures. ... Rounding rules for decimal numbers are as follows: ... Since the digit in the smallest place is less than 5, round down has to be done ... time definition physics · standard units.
For more information, see Rounding Off - Definition, Rules, Examples
Significant digits or significant figures are the reliable digits plus the first uncertain digit.
The rules for calculating the number of significant figures
a) 0.007 m^2
Significant figures = 1
b) 2.64* 10^{24} kg
Significant figures = 3
c) 0.2370 gcm^{-3}
Significant figures = 4
d) 6.230 J
Significant figures = 4
e) 6.032 Nm^{-2}
Significant figures = 4
f) 0.0006032 m^2
Significant figures = 4