Before any order is shipped, inspectors at Alvarez Manufacturing test a sample of finished units for breaking strength. You select a simple random sample of 49 units from a recently completed order and find that the sample average breaking strength is 789 pounds. Assume that the standard deviation of the breaking strengths for the population of units in the order is known to be 42 pounds. Construct a 90% confidence interval estimate of the average breaking strength you could expect to find if all the units in the order were tested.