How Often do The Vowel Rules Work

A-When There are two Vowel Letters in a Syllable:
1-The First Vowel Says its Alphabet Name.
2-The Second Vowel is Silent.
For Example: cake , tea , ice , cone , cube
B-When there is only one Vowel letter in a Syllable:
1-The Vowel Letter does NOT say its Alphabet name.
2-The Vowel Letter says its RELATIVE sound.
For Example: can , [...]