title: Calculate the cost per square of a circular object
body: <p>I am trying to calculate the cost per square of a circular object, given its diameter and price.</p>
  
  <p>Here is what I got:</p>
  
  <pre><code>import math
  
  def main():
      print("This program calculates the cost per square inch of a circular object.")
  
      diameter = eval(input("What is the diameter of the object? "))
      price = eval(input("What is the price of the whole object? "))
  
      cost_per_square = (math.pi * (diameter / 2)**2) / price
  
      print("The cost per square inch is $", round(cost_per_square, 2), sep="")
  
  main()
  </code></pre>
  
  <p>I'm not good at math, so I wondered if the formula is correct ?</p>