At your plant, your team ordered reinforcing bars for a reinforced concrete structure. From the delivered batch, 25 bars were randomly selected and tested for yield strength. The sample mean yield strength from these 25 tests was 37.5 psi. Assume that bar strength is Normally distributed, with an individual bar strength standard deviation of 3.0 psi. Which option correctly gives the expression and value for the standard deviation of the sample mean o&, and correctly states what uncertainty it represents