Crylic bone cement is sometimes used in hip and knee replacements to fix an artificial joint in place. The force required to break an acrylic bone cement bond was measured for six specimens under specified conditions, and the resulting mean and standard deviation were 305.09 Newtons and 40.67 Newtons, respectively. Assuming that it is reasonable to assume that breaking force under these conditions has a distribution that is approximately normal and using 95% confidence level, estimate the true average breaking force f for acrylic bone cement under the specified conditions.