How do I understand 能 in 请问几天能到? In the following dialogue:


  A: 小姐， 我想机一个包裹。
  B: 请问，寄到哪儿? 寄什么?
  .........


Then later A asks:


  请问几天能到?


What is 能 here, I cannot find the grammar. 

In my books 能 is for permission, to be able to do something, ‘be possible’ also express possibility, in the sense of someone being able to do something on a particular occasion.

But in this case is a question for the future, how long does it take the packet to reach. Can you not use 会?If you use 能, what is the exact grammar point?
A: &quot;小姐， 我想寄一个包裹。&quot; (Miss, I want to mail a parcel)
B: &quot;请问寄到哪儿? 寄什么?&quot; (May I ask, where are you mailing it to? And what you are mailing?)
.......
A: &quot;请问几天能到?&quot; (may I ask, in how many days can it arrive?)

能 = can ; 到 = arrive

几天能到? =  can arrive in how many days?

会 = would/will

几天会到? = would/will arrive in how many days?