(4aR,8aS)-Octahydronaphthalen-2(1H)-one (2-decalone, numbered C1 to C8 with ring-fusion carbons 4a and 8a, C=O at C2) is given. Using CIP rules, which statement is correct?

At C8a the priorities are C4a > C1 (leads to C=O) > C8 > H, and at C4a they are C8a > C4 > C5 > H. Working both centres through for the two ring fusions (with an explicit CIP check) gives like descriptors (4aR,8aR or 4aS,8aS) for trans-fusion and unlike descriptors (4aR,8aS or 4aS,8aR) for cis-fusion. So the given compound is cis-fused. It has no internal mirror plane because C1 and C4 are inequivalent (the C=O is at C2), so it is chiral and its enantiomer is (4aS,8aR).