Pedro has a stack of coins that weighs 85 grams. Conner has a stack of coins that weighs 64300 milligrams. Whose stack of coins weighs more and by how much?
a) Pedro's stack weighs more by 27 grams
b) Conner's stack weighs more by 31 grams
c) Pedro's stack weighs more by 64215 milligrams
d) Conner's stack weighs more by 64315 milligrams
