0 <= x <=       30 ; y =      58.0000 +       0.6333 x ; interpolation
      30 <= x <=       60 ; y =      94.0000 +      -0.5667 x ; interpolation
      60 <= x <=       90 ; y =      22.0000 +       0.6333 x ; interpolation
      90 <= x <=      120 ; y =     121.0000 +      -0.4667 x ; interpolation
       0 <= x <=      120 ; y =      64.6000 +       0.0533 x ; least-squares