Whether a defendant convicted of RICO conspiracy under 18 USC § 1962(d) is subject to enhanced sentencing under § 1963(a) based on a jury finding of agreement to join a RICO enterprise or only upon a jury finding that the substantive racketeering act was actually committed

A person is guilty of violating the Racketeer Influenced and Corrupt Organizations Act (“RICO”) if they violate any of subsections (a)-(d) under 18 USC § 1962. Pursuant to 18 USC § 1963(a), a RICO violation carries a sentence to a term of imprisonment of “not more than 20 years (or for life if the violation is based on a racketeering activity for which the maximum penalty includes life imprisonment).” Where a racketeering act amounts to a substantive crime that carries a maximum penalty of life imprisonment, but a racketeering act that amounts to a conspiracy to commit that substantive crime does not, whether a defendant convicted of RICO conspiracy under 18 USC § 1962(d) is subject to enhanced sentencing under § 1963(a) based merely on jury finding that defendant agreed . to join the RICO enterprise knowing that that members were conspiring to commit the racketeering act, or whether enhanced sentencing is permissible only upon a jury finding that includes a determination that the substantive racketeering act was actually committed? i