There started with 50 and it doubles so that means:
100 at the end of year 1
200 at the end of year 2
400 at the end of year 3
800 at the end of year 4
Answer:
The A option is correct since:

Good luck!
Intelligent Muslim,
From Uzbekistan.
I’m not sure I would help you if knew
Answer:
.214 if it is to 3 decimal places.