Kenneth R. Prentiss became the 29th postmaster of Salt Lake City Tuesday at a ceremony at the Main Post Office, 1760 W. 21st South. More than 250 postal employees and guests were on hand as Joseph R. Caraveo, regional postmaster general for the Western United States, gave Prentiss the oath of office. An 18-year veteran of the Postal Service and formerly postmaster of Colorado Springs, Colo., Prentiss will supervise the Salt Lake Division, which includes operations in Utah, Montana, most of Idaho and parts of Oregon and Nevada. The division handles nearly 1.4 billion pieces of mail a year.