What is the mandatory minimum sentence for possessing a firearm in furtherance of a crime of violence?

In Dean v. United States, 2017, No. 15–9260 (U.S.S.C.), the accused was convicted of two robberies in which a firearm was used and two counts of possessing a firearm in furtherance of a crime of violence, in violation of 18 U. S. C., section 924(c). Section 924(c) mandates a distinct penalty to be imposed “in addition to the punishment provided for [the predicate] crime” to be served on a consecutive basis. For a first conviction under section 924(c), a mandatory minimum period of five years imprisonment must be imposed. For a second conviction, an additional twenty-five year mandatory minimum is prescribed.