How did trade effect the abbasid dynasty?

How do conflict minerals, and in particular, conflict coltan get their name? what groups benefited from the trade in conflict minerals? what group were hurt by it?

When did paul zoll develop cardiac pacemaker

How did the completion of the transcontinental railroad change the lives of american citizens? a-it increased the wealth of all americans and enabled them to travel more. b-it made cross-country travel too expensive for ordinary americans. c-it decreased the safety of americans who moved to settle the plains. d-it shortened travel time between the east and west for all americans.