<image>4 equally heavy black pearls, 1 white pearl and a piece of iron weighing $30 \mathrm{~g}$ are placed on a beam balance as shown in the diagram. The beam balance is balanced. How heavy are 6 black and 3 white pearls altogether?
A. $100 \mathrm{~g}$
B. $99 \mathrm{~g}$
C. $96 \mathrm{~g}$
D. $94 \mathrm{~g}$
E. $90 \mathrm{~g}$