I'm studying stats independently so don't have a teacher to ask how to finish this question. Any help would be much appreciated.

Before being delivered, bags of lawn seed ar chosen at random from large batches and the contents weighed. The weight is known to be normally distributed with a standard deviation of 0.5kg.

A batch is accepted if the mean of 4 bags exceeds 24.8kg.

The manufacturer requires that the probability of accepting a batch with mean contents of 25kg should be at least 0.95. The garden centre requires that the probability of accepting a batch with mean contents of 24.6kg should be less than 0.01.

Question: Determine the minimum sample size and the weight which must be exceeded by the sample mean for a batch to be accepted.

I got n=17 and n=34 for the first part, but the answer book says n=25. I couldn't work out where to start for the second part. The answer is 24.84 but I don't know how to get there.