Normal Distribution problem

Hi There

I got stuck with below problem on Normal Distribution:

A forestry nursery in the Bay of Plenty plants Douglas fir seedlings. Those that survive are measured after five years, and it is found that their diameters are normally distributed, with a mean of 22 cm and a standard deviation of 2 cm.

Two trees are chosen at random.

- Calculate the probability that both tree measures under 20cm.
- Calculate the probability that one tree measures under 20cm and the other measures over 20 cm.

Kindly help me through this problem, I shall be very thankful to you.

Many thanks in advance.

Parveen