The drum of a photocopying machine has a length of $42 \mathrm{~cm}$ and a diameter of $12 \mathrm{~cm}$. The electric field just above the drum's surface is $2.3 \times 10^5 \mathrm{~N} / \mathrm{C}$. What is the total charge on the drum? 
$0.32 \mu C$