<prompt> Translate the following text to SwahiliPostal Service Productivity and Its Measurement, Staff Study of the Postal Rate Commission, May 9, 1990.  <response>: Utaratibu wa Uuzaji wa Posta na Upimaji wake: Utafiti wa Wafanyakazi wa Tume ya Kiwango cha Posta, Mei 9, 1990 