How do we compute DF and T-critical (Exampe #1)

Wanda Brunner, CFA, is trying to calculate a 95% confidence interval for a regression equation based on the following information: What are the lower and upper bounds for variable DR? The coefficient for DR is .52 The standard error is .23 My first question is: How do we know it’s a two tailed test? My second question is: How do we know what the DF are so we can compute T-critical? This is what they give as the answer: “The critical t-value is 2.02 at the 95% confidence level (two tailed test). The estimated slope coefficient is 0.52 and the standard error is 0.023. The 95% confidence interval is 0.52 ± (2.02)(0.023) = 0.52 ± (0.046) = 0.474 to 0.566”