Kylie is preparing for the science fair which will take place in six weeks. She has three plants that she has grown from seeds, which she considers to have height 0 centimeters, and she is measuring their heights as she applies different treatments to each. The third plant is planted in the same soil as the others, but it receives only light and water. After 2 weeks, it is 6 centimeters tall. If it continues growing at this rate, how tall will it be after 6 weeks?

For every corresponding pair of cross sections, the area of the cross section of a sphere with radius r is equal to the area of the cross section of a cylinder with radius and height 2r minus the volume of two cones, each with a radius and height of r. a cross section of the sphere is and a cross section of the cylinder minus the cones, taken parallel to the base of cylinder, is the volume of the cylinder with radius r and height 2r is and the volume of each cone with radius r and height r is 1/3 pie r^3. so the volume of the cylinder minus the two cones is therefore, the volume of the cylinder is 4/3pie r^3 by cavalieri's principle. (fill in options are: r/2- r- 2r- an annulus- a circle -1/3pier^3- 2/3pier^3- 4/3pier^3- 5/3pier^3- 2pier^3- 4pier^3)