Using a sample of 69 quarters of sales, you carry out an AR(1) model regression, and produce the following results: To test for serial correlation of errors, you find that the first order error autocorrelation is 0.12. What is the t-statistic to test it for significance? Hint: note that your regression sample is 1 less than your original data, since you lose one observation to the lag (i.e. there is no previous-quarter data point for the very first quarter in our sample)