in reported speech "it" is changed into "that"
customer-:can i have a bottle of juice?
shopkeeper:-sorry,we have only milk bottles
c:-when will it be available?
s:-i can give it to you tomorrow.
change into indirect
the customer asked the shopkeeper(a)-------
the shopkeeper apologized and said(b)--------
the customer wanted to know(c)------------
i have doubt in (c)
according to me its answer is
when it would be available