An agreement may be found to be lacking in consideration if:

a$.$ It is based on a preexisting duty that may have been imposed by law or have risen out of a previous contract,

b$.$ It is based on a promise made in return for actions or events that have already taken place.

c$.$ The terms of the contract express such uncertainty of performance that the promisor has not definitely promised to do anything.

d$.$ All of the above.