Draw a figure with the given perimeter of 10 units

With every side = 2.5
s
i will draw a square 
     
      2.5
      |                        |
      |                        |
2.5 |                        |  2.5
      |                        |
     
                2.5 

now add those together 
2.5 + 2.5 + 2.5 + 2.5 = 10 
ANSWER = 2.5units

The answer is that the rate of change is $50 per 1 monthhope this ; )