A researcher fits a regression model and obtains an estimated slope $\hat{\beta}_1 = 2.50$ with a standard error of $s_b = 0.50$. She wants to test the null hypothesis $H_0: \beta_1 = 1.00$ against the alternative hypothesis $H_a: \beta_1 \neq 1.00$. What is the calculated $t$-statistic for this test?