I'm a little confused by this problem:

Let D = {2, 3, 6, 8, 9, 10, 12, 15, 18, 20} and R is the partial order relation defined on D where a R b means a | b.

Find the requested elements if they exist.

1. The lub({3,10})

2. The lub({2, 9})

3. The glb({12, 10})

My answers:

1. lub({3,10}) does not exist.

2. The lub({2, 9}) = 18.

3. The glb({12, 10}) = 2.

Am I doing this correctly? Any suggestions are welcome.