title: Override setArea class and multiply the value
body: <p>I have to override this class which is in Geometric Shape.h:</p>
  
  <pre><code>- (void) setShapeArea:(NSNumber *)shapeArea
  {
      _area = shapeArea;
  }
  </code></pre>
  
  <p>I have another class called rectangle. I am supposed to override area method to correctly return the area of a rectangle. This is what I wrote in my rectangle.m class:</p>
  
  <pre><code>-(void)setShapeArea:(NSNumber*)shapeArea
  {
      shapeArea = (_width * _height);
  }
  </code></pre>
  
  <p>which is giving me an error.</p>
  
  <p>I am not sure how to move along with this. </p>