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§3.1, Eq. (10): the coordinating target T(u)T(u)T(u), admissible iff u>m+δm(w−c)u > m + \delta_m(w-c)u>m+δm​(w−c)

Proved
FalseFailureReturns.TargetRebate.coordinating_target_iff

by mikedeng1 · Sep 28, 2026 · Mathlib 0df444a (Lean v4.33.1)

contractsp2o-batch-p200bp2o-gran-per-chapterp2o-plan-paperp2o-v1principal-agentsupply-chain

Let a>0a > 0a>0, β>0\beta > 0β>0, Mm>0M_m > 0Mm​>0, Rr>0R_r > 0Rr​>0 with (Mm+Rr)β>a(M_m + R_r)\beta > a(Mm​+Rr​)β>a, and let X(ρ)∼Uniform(0,2β/ρ)X(\rho) \sim \mathrm{Uniform}(0, 2\beta/\rho)X(ρ)∼Uniform(0,2β/ρ). For a target rebate contract with u>0u > 0u>0 and T>0T > 0T>0 the following are equivalent:

  1. (u,T)(u, T)(u,T) coordinates the supply chain (the coordinated effort ρC\rho^CρC maximizes πR(⋅∣T,u)\pi_R(\cdot \mid T, u)πR​(⋅∣T,u) over ρ≥1\rho \ge 1ρ≥1) and satisfies T<2β/ρCT < 2\beta/\rho^CT<2β/ρC;
  2. TTT is given by
T=2β2/3a1/3Mm1/2u1/2(Mm+Rr)1/3(10)T = \frac{2\beta^{2/3}a^{1/3}M_m^{1/2}}{u^{1/2}(M_m + R_r)^{1/3}} \tag{10}T=u1/2(Mm​+Rr​)1/32β2/3a1/3Mm1/2​​(10)

and u>Mm=m+δm(w−c)u > M_m = m + \delta_m(w - c)u>Mm​=m+δm​(w−c).

In words: for each rebate uuu there is exactly one admissible coordinating target, and it exists precisely when the rebate exceeds the manufacturer's own profit of avoiding a false failure return. In particular coordinating contracts with T<2β/ρCT < 2\beta/\rho^CT<2β/ρC exist, so the hypotheses of Proposition 2 can be met.

Preamble
import Mathlib
import Definitions.Def_FalseFailureReturns_TargetRebate_Model
import Definitions.Def_FalseFailureReturns_TargetRebate_UniformRebate
Formal statement
namespace FalseFailureReturns.TargetRebate

theorem coordinating_target_iff (P : Params) (T u : ℝ)
    (ha : 0 < P.a) (hβ : 0 < P.β) (hM : 0 < P.Mm) (hR : 0 < P.Rr)
    (hint : P.a < (P.Mm + P.Rr) * P.β) (hu : 0 < u) (hT : 0 < T) :
    (Coordinates P T u ∧ T < 2 * P.β / coordEffort P) ↔
      (T = 2 * P.β ^ ((2 : ℝ) / 3) * P.a ^ ((1 : ℝ) / 3) * P.Mm ^ ((1 : ℝ) / 2) /
          (u ^ ((1 : ℝ) / 2) * (P.Mm + P.Rr) ^ ((1 : ℝ) / 3)) ∧
        P.Mm < u) := by sorry

end FalseFailureReturns.TargetRebate
Source
Ferguson, Guide & Souza, Supply Chain Coordination for False Failure Returns, MSOM 8(4) 2006, p. 383, §3.1, Eq. (10)
Human review
  • Endorsed by Shuze Chen · Oct 1, 2026

    Confirmed by the moderator at approval.

  • Endorsed by mikedeng1 · Oct 1, 2026

    Confirmed by the mission captain (proposal self-audit).

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