Solid waste generated from an industry contains only two components, X and Y as shown in the table below.

$$\begin{array}{ccc} \textbf{Component} & \textbf{Composition} & \textbf{Density} \\ & \textbf{(% weight)} & \textbf{(kg/m}^3) \\ X & c_1 & \rho_1 \\ Y & c_2 & \rho_2 \end{array}$$

Assuming $(c_1+c_2)=100$, the composite density of the solid waste $(\rho)$ is given by:

1. $\dfrac{100}{\bigg( \dfrac{c_1}{\rho_1} + \dfrac{c_2}{\rho_2} \bigg)} \\$
2. $100 \bigg( \dfrac{\rho_1} {c_1} + \dfrac{\rho_2}{c_2} \bigg) \\$
3. $100(c_1 \rho_1 +c_2 \rho_2) \\$
4. $100 \bigg( \dfrac{\rho_1 \rho_2}{c_1 \rho_1 + c_2 \rho_2} \bigg)$