Since the sample size, , is sufficiently large (greater than 30), you can go ahead and use Z instead of t with 49 df. If this concept does not make sense to you, familiarize yourself with the Central Limit Theorem. Note that the table values for Z and for t with 49 df will be very close to one another.
That said, your confidence interval takes on the form . Since you know , , , and , computing your desired confidence interval is straightforward.