Size Reduction and Milling

Bond's law states that energy required for size reduction is $P = 10 W_i \left(\frac{1}{\sqrt{d_2}} - \frac{1}{\sqrt{d_1}}\right)$, where $d$ is in microns and $W_i$ is Bond's work index in kW$\cdot$h/tonne. If $W_i = 12\text{ kW}\cdot\text{h/tonne}$, $d_1 = 2500\;\mu\text{m}$ ($\sqrt{d_1} = 50$), and $d_2 = 100\;\mu\text{m}$ ($\sqrt{d_2} = 10$), the power required to grind 10 tonnes/h of feed in kW is: