The correct option is A 12 mm
Circumcircle radius = abc4×√s(s−a)(s−b)(s−c)
Where, area of the triangle = √s(s−a)(s−b)(s−c)
a=b=c (Since the triangle is equilateral)
abc= a3
So, 2×4×8= a3
64= a3
a=4 mm
One side of the triangle =4 mm
So, perimeter of a equilateral triangle =3×4=12 mm