rs to (a) and (b), for what range of values of t statistics would the hypothesis test conclusion differ between using the t or normal critical values?...

Comparing the answers to (a) and (b), for what range of values of t statistics would the hypothesis test conclusion differ between using the t or normal critical values? How practically important does this difference appear to be? Explain.

Given that n=60, H0: mean=0, HA: mean>0, level of significance=0.05 and:

(a) Using t distribution in excel, critical value=1.671

(b) Using the table(since the df>30, so we use df=infinity), critical value=1.645