K : Competitiveness (aka Performance)
Ea : Efficacy
Ei : Efficiency
Qp : Quality of Product
Qs : Quality of Service
T : Time
C : Cost
Ea =def Qp * Qs
Ei =def 1 / (C * T)
K =def Ea * Ei = (Qp * Qs) / (C * T)
The definition of competitiveness is common to all kinds of engineering, but with software (in fact, with all knowledge-related production), contrary to what happens with conventional engineering (the "hard" kinds of production), efficacy and efficiency are directly proportional. In other words, and contra the usual assumptions, with software, higher quality goes with lower costs. In symbols:
Ea ∝ 1/Ei for "hardware" Ea ∝ Ei for "software"