Statistics help please.

Hi all. No... I don't want you to do my homework for me. But please, help teach me how to do this. It's for an intro Statistics class.

Suppose a simple random sample of size n = 36 is obtained from a population with u (mean) = 64 and o (std. dev.) = 18.

a)describe the sampling distribution of X (sample mean).
b)What is P(x < 62.6)?
c)What is P(x > or = to 68.7)?
d)what is P(59.8 < X  < 65.9)?

Please help walk me through this so i can see how it is done.
The X is actually the X with the line over it for the sample mean.

k. in your graphing calculator, hit 2nd vars (for dist menu). select normcdf. lower limit is the lowest #. if you are asked P(x<10) then your lower limit is infinity ( enter 1ee99 by hitting 1, ee ( which is 2nd then the comma button) then 99) enter your upper limit (10) enter your mu, then enter your o.
if you are asked P(x>10) then your lower limit is 10, your upper limit is infinity, enter your mu, then your o.

if you are asked p(10>x>20) then your lower limit is 10, upper limit is 20, then enter your mu and o.

im doing the exact homework you are doing right now, so i hope this helps.