Probability with broken drainpipes
Sorry again for a vague-ish title - I have no clue where to begin with this.
To check the quality of plastic drainpipes a manufacturer selects 10 pipes at random from each large production batch and subjects them to an impact test. Flawed pipes break on the test but good ones do not. If more than two pipes on test break, the whole batch is scrapped. What are the probabilities:
a) that the batch will be scrapped when only 5% of the pipes in it are flawed;
b)that the batch will not be scrapped even if the proportion of flawed pipes is 25%?
There doesn't seem to be enough numbers here; I'm clearly missing something.