When the degree of freedom is infinite then we say that the distribution is normal distribution and t score is nothing but the Z score. So Z score = 1.55.

For two tail test if test statistic is between t_{α/2} and t_{(1-α/2) } critical score then we fail to reject the null hypothesis. If the test statistic is not between t_{α/2} and t(_{1-α/2)} then we reject the null hypothesis.