Mean and Standard Deviation....

Alright, I am working a problem, can't quite figure out how we arrive at the answer in the book-

Here it goes:

Specifications for a part for a dvd player state that the part should weight between 24 and 25 ounces. The process that produces the parts yields a mean of 24.5 ounces and a standard deviation of .2 ounces. The distribution of output is normal.

a) What percentage of parts will not meet the weight specs?

b) Within what values will 95.44% of sample means of this process fall, if samples of n=16 are taken and the process is in control (random)?

I figured on a) that we would use the z= x-m(mu)/standard deviation....but I'm not sure where I am going with this.

Can anyone help me with this? I'm not understanding how to arrive at any real "answer".

Thanks!!(Thinking)