(2)A=P_n*2000+0.7P_n*(8760-2000)=6732Pn  

         T_MAX=A/P_MAX=6732P_n/P_n=6732h  

      (3) Δ A= ×Δ P_k × 2000+ ×Δ P_k × (8760-2000)+P₀ × 8760

          = × 220 × 2000+0.6² × 220 × 6760+86 × 8760=1729292kWh  

    2.

      _D1= _a-jX_{D1 D1}

      _D2=-jX_{D2 D2}

      _D0=-jX_{D0 D0}  

     ③ _D1=- _D2

       _b=a² _D1+a _D2=-j _D1

       _c=- _b=j _D1