Diamond patterns II

This task is about completing a pattern and writing a rule to describe the pattern.

a) Draw the next two patterns in this series of diamonds.
 
b)
 
Complete this table.
 

Shape number

1

2

3

4

5

Number of shaded squares

4

8

12

   
 
c)
 
How many shaded squares would there be in
 
i)     shape number 20? __________
 
ii)    shape number 50? __________
 
d)
Complete this rule to show how many shaded squares make up diamonds of various sizes.
 
The number of shaded squares = the shape number ___________________________