Consideration

A bill of exchange! These used to be in the English syllabus and they still are in the global syllabus

By definition:

A bill of exchange is an unconditional order in writing, addressed by one person to another, signed by the person giving it requiring the person to whom it is addressed to pay on demand or at a fixed or determinable future time a sum certain in money to, or to the order of, a specified person or to bearer

It’s basically an instruction (to the bank, more often than not) to pay a creditor

Say you buy goods (or services) and you don’t pay straight away … instead you give the supplier a piece of paper that satisfies the definition of a bill of exchange

The bill will have a period of time specified – Pay 90 days after date …

After 90 days, that bill has matured and is due for payment. But your bank refuses to pay it – maybe not enough funds in your account

So the creditor sues you

You claim that the bill is not enforceable because the goods that you received were delivered 90 days ago and past consideration is no consideration

Won’t work, sorry. Bills of exchange are an exception to that rule

That actually explains the first 2 from your list

I’d like the full context for the third one on your list – does the text not give you a bit of explanation?

Hmm, ok. Because there is an implied promise to pay, the subsequent promise of a reward is merely taken as confirmation of the amount of the earlier implied promise

NB in practice it is always safer to agree on ALL major terms before starting to discharge your end of the agreement!