Consideration will be sufficient to establish a contract where:

a. the price paid by the promisee is a vague promise to do something or refrain from doing something.

b. the price paid for the promise had been paid before the promise was made.

c. the price paid by the promise was the fulfilment of a prior legal obligation, that is, the performance of something the promise was already legally obligated to do.

d. the price paid has been some legal value even if it is not a fair or adequate price.