Imagine that we receive a message, but we won't have the information to provide a complete answer for at least $3$ days.

In this case, we should:

Select one:

a$.$

Wait until we receive the information needed to provide a complete reply.

b$.$

Reply within our regular email turnaround time letting the sender know we can't answer their question.

c$.$

Reply within our regular email turnaround time letting the sender know we'll have their reply in a few days.

d$.$

Wait at least $48$ hours and then email the sender that we will have a reply in a few days. Waiting shows that we tried to get the info needed.