GOOD - The currency has been changed from JPY to USD.( on the business contract.)
- l got off work at 9 p.m. yesterday, whereas you left WORK/ left the OFFICE at 5 p.m.
(We normally say "get off work" when we are leaving earlier than usual, and so you could reverse the two times.)
GOOD - Such a large investment entails some risks.
GOOD but unusual. -This essay entails writing 20000 words. Entail is used in more formal situations than this one.
GOOD - This job involves spending long hours at the office. Can you stand it?
GOOD - There are too many politicians involved in this scandal.
- They are a black enterprise. We should resist/AVOID buying their products.
"Black enterprise" is not a standard collocation but we can guess that it is a bad one. Perhaps "illegal", "corrupt", "black market"? Enterprise is not commonly used for specific commercial entities. "Business" is the common generic word.