Building square patterns

This task is about making a pattern and describing a rule.
          Y   /   N
a) Use 4 rods to make the smallest square you can.
b) i) Now use more rods to make a square the next size up.
  ii)
 
How many rods did you use for the second square?   __________
 
c) i) Now use more rods to make a square the next size up again.
  ii)
 
How many rods did you use for the third square?   __________
 
d) i) How many rods would you need for a fourth square?   __________
  ii)
How did you work this out?