Answer is A-photosystem II
6.4 * 6.02 * 10^23 = 3.8528*10^24 atoms
Don't let the fact that it's vanadium throw you off, avagadros constant stays the same for all elements
The density of the block will be "7.11 gm/cm³". A further explanation is provided below.
Given values are:
Density of iron,
Mass of block of metal,
Volume of block,
By using the formula,
→ 
then,
→ The density of block will be:
= 
= 
= 
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I believe so, looks like it