A bioengineer wants to model the amount (y) of carbohydrate solubilized during

A bioengineer wants to model the amount (y) of carbohydrate solubilized during steam processing of peat as a function of temperature (x1), exposure time (x2), and pH value (x3). Data collected for each of 15 peat samples were used to fit the model 

E(y)  =βo + β1x1 + β2x2 + β3x3

A summary of the regression results follows: 

Based on these results, the bioengineer concludes that none of the three independent variables, x1, x2, and x3, is a useful predictor of carbohydrate amount, y. Do you agree with this statement? Explain.