A circle is rotated around a vertical line which we call Y axis.
When we rotate the circle around y axis, and join each circle ,we get a closed shape resembling with the Cylinder, having height equal to Diameter of circle.
We can't Calculate Radius of shape resembling with Cylinder.
For a "want" like a TV, she should have an amount in the spending section. She is trying to save, so she shouldn't waste her money on something that is not a necessity. She still has 90% left of her checks, so she has that money. She could use that.