I does help the network, but whether it's worthwhile is up to you. As far as efficiency, a laptop cpu is going to be terrible.
It definitely doesn't help, until they find a block, given the difficulty that is nearly impossible.
It does help, simply because they could find a block. Like raindrops form a river, every little contribution strengthens the blockchain a little. If we look at it like you are, then we should stop all this other wasteful searching and just look in the last place we would have!
Not at all. Yes, it COULD help, but given how bleak the likelihood of them finding a block is within a reasonable amount of time for the power expended, it approaches minimal usefulness, and is essentially zero. It's far better to avoid wasting the energy to begin with, and to avoid the wear on the poor CPU.
