Introduction to Logic

Exercise 1.4 - Logical Reasoning

Say whether or not each of the following rules is logically correct.

a.
All x are z.
All y are z.
Therefore, some x are y.
   
b.
Some x are y.
All y are z.
Therefore, some x are z.
   
c.
All x are y.
Some y are z.
Therefore, some x are z.