<prompt> Translate the following text to EnglishSheria ya 504 a iliruhusu Mkuu wa Postmaster kudumisha programu ya utafiti na maendeleo, na kufanya majaribio ili kuongeza ufanisi wa uendeshaji na uchumi wa mfumo wa posta.  <response>: Rule 504a authorized the Postmaster General to maintain a research and development program, and to conduct experiments to enhance the operational efficiency and economy of the postal system. 