Use the Given Information to Find the Minimum Sample Size $\mu$

Use the given information to find the minimum sample size required to estimate an unknown population mean $\mu$
-How many commuters must be randomly selected to estimate the mean driving time of Chicago commuters? We want 90% confidence that the sample mean is within 4 minutes of the population mean, and the population
Standard deviation is known to be 12 minutes.

A) 60
B) 25
C) 35
D) 49