The characteristics of two types of solid waste are given in the table.
The quantity of sludge to be added to leaves to achieve a $\mathrm{C} / \mathrm{N}$ ratio of $25$ (on dry basis) for the mixed waste is $\_\_\_\_$ $\mathrm{kg}$ of sludge/kg of leaves (rounded off to three decimal places).
| Type of solid waste | Characterstics of the solid waste (weight/weight) |
| Moisture content ($\%$) | Nitrogen content ($\%$) | Carbon to Nitrogen (C/N) ratio |
| Leaves | $50$ | $0.7$ | $50$ |
| Sludge | $75$ | $5.6$ | $6.3$ |
