Robert was walking around the camp looking at various nooks and crannies. He needed some more bullets for his gun and a sharpening stone for his sword. He walks up to a merchant and asks about bullets. "Twenty should be enough"
 
"That'll be 5 bronze." The merchant replies.

"You wouldn't happen to have a sharpening stone as well?" Robert replies

"Yes, I have one right here. That would be 15 bronze" The merchant says.

"Thanks sir!" Robert says while fumbling in his pockets after the coins. He put the sharpening stone in his backpack and the bullets in his satchel. He then walks over to another merchant to buy all of the other stuff he needs.