Answer:
See below.
Explanation:
Helen made a mistake in the last step.
2^(4/3) / e = (∛(2^4) / e = ∛(16) / e .
It is the cube root of 2^4 not the 4th root of 2^3.
Stephen made a mistake in the first step.
He replaced ln2 by 2 which is evidently wrong (e^ln2 = 2 NOT ln 2).