You don’t need to do any Math. That’s a waste of time. Just estimate.
8 square root 3 is approx equal to 14. That represents the total length of the belts extending from the small circle to the large circle. Each one is approx 7.
If you look at the line marked “8”, then you know that the belts are about the same length as that line marked “8”.
The other answers are either too small or too big.