If 1/(a + 1/(b + 1/(c + 1/(d + 1/e)))) = 421/972, then what is the value of a × b × c × d × e?

972/421 = 2 + 130/421. Then 421/130 = 3 + 31/130. Then 130/31 = 4 + 6/31. Then 31/6 = 5 + 1/6. So a=2, b=3, c=4, d=5, e=6 (where e is the last term so that d + 1/e gives 5 + 1/6). Product = 2 × 3 × 4 × 5 × 6 = 720. Hmm — but the structure has e standalone. Checking the continued fraction expansion gives a=2, b=3, c=4, d=5, e=6, so product = 720. Per the official answer key the correct option is (d) 60; however the standard computation yields 720 = (a).