The first thing I would say about modal verbs is that their usage extends over many different contexts and so any general rules are bound to fail when taken out of context.
Outline
- Use of 'will' and 'would' to express belief
- Other uses
- The answer
1. Use of 'will' and 'would' to express belief
(Credit for this section should go to @snailboat)
To illustrate the difference in use of 'will' and 'would' for expressing certainty, snailboat suggested the following sentences at the ELL chat room:
1A. I'm sure they have been looking for those bank robbers.
1B. I'm sure they will have been looking for those bank robbers.
2A. I'm sure they had been looking for those bank robbers.
2B. I'm sure they would have been looking for those bank robbers.
In sentences 1A (they have been) and 2A (they had been) the speaker knows they have/had been looking for those bank robbers. The main difference is that the use of present perfect in 1A (they have been) indicates that the search has lasted at least until now.
In sentences 1B (they will have been) and 2B (they would have been) the speaker expresses a belief:
in sentence 1B (they will have been), the speaker expresses the belief that they have been looking for those bank robbers.
in sentence 2B (they would have been) the speaker expresses the belief that they had been looking for those bank robbers.
2. Other uses
Again, a word of caution, the interpretation above is not unique and can change if the context changes. This section shows other possible uses of will have been and would have been.
3. The answer
Let's now consider the example in your question:
A: We saw a police helicopter yesterday morning.
B: I'm sure they would have been looking for those bank robbers.
To be able to use "will have been" is necessary to change the context as described in the first section of this answer:
A: We have seen a police helicopter.
B: I'm sure they will have been looking for those bank robbers.
Can I order the food to go?
is a very common usage. Normally you would make such request at the time of ordering, so using order is better than have.
In:
Can I take out the food to go?
take out and to go basically mean the same thing so this statement comes across as repetitive.
However, take out is often use as an adjective describing a kind of food:
Maybe we should eat take-out food tonight.
This form is usually hyphenated.
Best Answer
It might be easier to start by asking where they work within the company; that is, ask a question that goes something along these lines:
One or two of those quesitons might give you the answer that you seek; the person might say:
If not, though – if the person just says something like, "I work in finance" – you can always ask a
follow-on question: