How useful are Source A and B for an equiry into Russian defeats in WW1?

Source A is useful because it suggests that there isn't enough bullets and bombs because there were not enough metal so the mills could not supply these items. This is shown by that they were short of bullets. They also needed more medical supplies. And another reason for their lack of bullets was their lack infrastructure, they did not have enough steelworks for makig those products. Source A is a reliable source because it was a letter written by the Tsar to his wife in July 1916 because he is information back to his wife who was running…