\(\Sigma t_i=\left(258.6\right)^2+\left(273.6\right)^2+\left(289.7\right)^2+\left(308.9\right)^2+\left(331.0\right)^{^2}\)
\(+\left(355.0\right)^2+\left(377.1\right)^2+\left(400.4\right)^2=859,186.79\)
\(\left[\Sigma t_i\right]^2=2594.3^2=6'730,392.49\)
\(b=8\frac{\left(1'263,227.79\right)-\left(3814.7\right)\left(2594.3\right)}{8\left(859,186.79\right)-\left(6'730,392.49\right)}\)
\(b=\frac{209.346.11}{143,101.83}=1.462917071\)
\(X=381.7+402.2+426.5+454.3+486.5+520.2+553.3+590.0\)\(\)
\(=\frac{3814.7}{8}=476.8375\)
\(t=258.6+273.6+289.7+308.9+331.0+355.0+377.1+400.4\)
\(=\frac{2594.3}{8}=324.2875\)
\(a=X-Bt\)
\(=476.8375-\left(1.462917071\right)\left(324.2875\right)=2.431780338\)