According to Building Science for a Cold Climate, the mechanical and electrical equipment in many modern buildings accounts for how much economic cost? Question 8 options: a) less than one-tenth of their initial cost, as well as a small annual operating cost b) none of their initial cost, but substantial annual operating costs c) more than one-third of their inital cost, and no annual operating cost d) more than one-third of their initial cost, as well as a substantial annual operating cost