i need to find the confidence interval

TRY: You randomly select 18 adult male athletes and measure the resting heart rate of each. The sample mean heart rate is 64 beats per minute, with a sample standard deviation 2.5 beats per minute. Assuming the heart rates are normally distributed, should you us the standard normal distribution, the t - distribution, or neither to construct a 90% confidence interval for the population mean heart rate? Explain