Probability vs Grammar

Pleae help! I have a problem with the difference in meaning between two sentences. I'll give you the two sentences. Then after the two sentences, please read and answer my query. Here are the two sentences:

1. David broke his leg whilst he was ice skating.
2. Mr and Mrs Brown were watching their favourite program on television when suddenly the light went out.

Here is the query:

a. Did David continue ice skating after he broke his leg? Yes/no/maybe
b. Did Mr and Mrs Brown continue watching television after the light went out? Yes/no/maybe

A very popular course book said, in a very similar context, that the answer to question a is "no" and the answer to "b" is "maybe". I think this course book is wrong.

Surely, from a grammatical stand point, the answer to both questions is "maybe". After all. there is no way we can know for definite whether David stopped or carried on ice skating any more than we can know whether the Browns carried on watching T.V.. The only explanation I have for the book is that of mere probability: "How could David have carried on ice skating with a broken leg?". But this is not a solid grammatical argument, especially when you're standing in front of a class full of upper ints. My students would not buy the explanation, "Oh, David broke his leg so he couldn't continue ice skating." They would just came up with loads of reasons why he could have continued ice skating. I would agree with them.

O.K., Fine. The chances of David being able to continue ice skating with such an injury are pretty slim; but isn't it possible he carried on skating, then after a few minutes of agonizing pain thought, "Shit, I've brokeon me leg!"? Isn't it possible someone helped him round the rink the last few times? Isn't it just possible he was on herroine and didn't feel a thing? (Now I sound like Henry Fonda in Twelve Angry Men.)

In my opinion There's -no- grammatical difference between the two sentences in terms of what happened after the intervening event.

Who's correct: me or the book?