I might have made the image shabbier, but really wanted to know where I went wrong with my steps.

gn; r=5 and equi. triangle and regular pentagon inscribed in a circle.

arc_length AB = angle subtended to the center/360 * 2* pi * r

To find angle subtended by both A & B, through regular polygons and angles formula, deduced that half of B is 54 and half of A is 30.

Now drawing a line from A to B to complete imaginary triangle.

ā angle subtended by center is 96 deg

now 96/360 * 2* pi *5 = 8 * pi/3 which is > 2 * pi /3

So chose choice A. but turns out answer is C

help me out on this! thanks in advance