Using the Ordinary Least Squares (OLS) method, a researcher estimated the relationship between initial salary ($S$) of MBA graduates and their cumulative grade point average (CGPA) as $\hat S_i=\hat\beta_0+\hat\beta_1\,CGPA_i,\ i=1,2,\ldots,100$, where $\hat\beta_0=4543$ and $\hat\beta_1=645.08$. The standard errors of $\hat\beta_0$ and $\hat\beta_1$ are $921.79$ and $70.01$, respectively. The $t$-statistic for testing the null hypothesis $\beta_1=0$ is _____{(round off to two decimal places)