An investigator compares the durability of two different compounds used in the manufacture of a certain automobile brake lining. A sample of 132 brakes using Compound 1 yields an average brake life of 46,505 miles. A sample of 162 brakes using Compound 2 yields an average brake life of 46,122 miles. Assume that the population standard deviation for Compound 1 is 4464 miles, while the population standard deviation for Compound 2 is 1468 miles. Determine the 98% confidence interval for the true difference between average lifetimes for brakes using Compound 1 and brakes using Compound 2. Step 1 of 3: Find the point estimate for the true difference between the population means.