n - k                        = 504
s  (D.T. de la regresion)    = 6620,8652   Gretl: 6620,8652
||x - xbar||                 = 15,7888
ee(b2) = s/||x - xbar||      = 419,3385   Gretl: 419,3385
t = b2/ee                    = 21,7475
valor critico t_c (5%)       = 1,9647
valor p                      = 1,87e-74
IC 95%: [8295,68 ; 9943,42]