i think the circumference is 75.04, because:
the formula for radius when you only have the diameter is d / 2, so:
23.9 / 2
= 11.95
now that we have our radius, the formula for circumference is:
2 x r x π
so,
2 x 11.95 x 3.14 = 75.04
...at least that’s what i got.