A student determines the volume of a cork. He first pours some water into a measuring cylinder and then adds one glass ball. Next, he places the cork and then a second, identical glass ball into the water, as shown. Diagram 1 shows the initial water level. Diagram 2 shows the water level after the first glass ball is added. Diagram 3 shows the water level after the cork and the second glass ball are added. What is the volume of the cork?
- A$30\,\text{cm}^3$
- B$40\,\text{cm}^3$
- C$50\,\text{cm}^3$
- D$100\,\text{cm}^3$