0 <= x <=       30 ; y =      61.0000 +       0.6333 x ; interpolation
      30 <= x <=       60 ; y =      98.0000 +      -0.6000 x ; interpolation
      60 <= x <=       90 ; y =      20.0000 +       0.7000 x ; interpolation
      90 <= x <=      120 ; y =     128.0000 +      -0.5000 x ; interpolation
       0 <= x <=      120 ; y =      67.4000 +       0.0567 x ; least-squares