Check when a current loop looks like a dipole

A circular loop of radius a carries steady current I. At an axial point x = 2a, compare its exact field μ0Ia²/[2(a²+x²)^(3/2)] with the far-field dipole estimate μ0Ia²/(2x³).

What is Bdipole/Bexact at this point?

Organize the givens & assumptions

x = 2a
Same loop, current and axial point
Both formulas stated

Thin circular loop in vacuum with steady current. The dipole expression is an approximation whose accuracy at the stated point is being tested, not presumed.

A $1$
B $\frac{8}{5\sqrt5}$
C $\frac58$
D $\frac{5\sqrt5}{8}$

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