An ecology student investigated the rate of decomposition of two organic materials (oak leaf litter and cellulose filter paper) in a controlled forest soil environment over a period of 15 weeks. Both samples started with a mass of 250 grams.
The mass of each sample was recorded every 3 weeks, as shown in the table below:
| Time (weeks) | Mass of oak leaf litter (g) | Mass of cellulose filter paper (g) |
|---|---|---|
| 0 | 250 | 250 |
| 3 | 228 | 220 |
| 6 | 202 | 180 |
| 9 | 171 | 134 |
| 12 | 135 | 85 |
| 15 | 92 | 30 |
Calculate the rate of decomposition of the cellulose filter paper between week 3 and week 12. Give the unit.
