The mean response is (α₀+μ)+α₁t+α₂t². The three polynomial design columns have full rank,so least squares estimates α₁,α₂ unbiasedly. But replacing (α₀,μ) by (α₀+c,μ−c) leaves the entire data law unchanged,so neither separate parameter is identifiable or can have an unbiased estimator for all values. **A,B**.
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