translate English to French: (b) Eliminate the need for new structural slab openings and the closing of old slab openings for primary air duct risers and the need for constructing a new penthouse at rooftop for new mechanical equipment that was also eliminated: ($4 million).
b) Éviter de percer des ouvertures dans les dalles porteuses et de boucher les vieilles pour faire passer les conduites d'air ascendantes.