[Maybe his dry attempt at humor earlier made her wonder if she could get his buy-in on something like this... or his willingness to yes-and their situation takes her by surprise. Either way, it would be a poor showing to fail to roll with it, when he's done such a good job adapting.]

Wheels are gonna have shit-all for traction on the floor if it's fully frozen over... so our ride's only good until the end of the stacks.

[Though it sounded like an unhinged and offhanded joke of a suggestion, she's put more thought into the actual logistics of hastening their escape by book cart than it might have seemed from the initial comment.] Worth?