Figure 1 shows a graph of the volume of carbon dioxide gas produced during the reaction between calcium carbonate and dilute nitric acid over time.

| Time (seconds) | Volume of carbon dioxide (cm3\text{cm}^3cm3) |
|---|---|
| 0 | 0 |
| 15 | 32 |
| 30 | 54 |
| 45 | 68 |
| 60 | 76 |
| 75 | 81 |
| 90 | 83 |
| 105 | 83 |
| 120 | 83 |
State the total volume of carbon dioxide gas produced in the first 45 seconds.