coin - n. a small, flat, and usually round piece of metal issued by a government as money

seal - n. an official mark that is stamped on paper or on a small piece of wax to show that something (such as a document) is genuine and has been officially approved

challenge - n. a difficult task or problem : something that is hard to do

certainly - adv. without doubt

appropriate - adj. right or suited for some purpose or situation

gross - adj. rude or offensive

input - n. advice or opinions that help someone make a decision