A lemon loaf completely fills a pan measuring $20 \mathrm{~cm}$ by $18 \mathrm{~cm}$ by $5 \mathrm{~cm}$. The loaf is cut into 25 pieces of equal volume. If the density of the loaf is $2 \mathrm{~g} / \mathrm{cm}^{3}$, how much does each of the 25 pieces weigh?
(A) $72 \mathrm{~g}$
(B) $288 \mathrm{~g}$
(C) $36 \mathrm{~g}$
(D) $144 \mathrm{~g}$
(E) $720 \mathrm{~g}$
Since the loaf is cut into 25 pieces of equal volume, the volume of each piece is $\frac{(20 \mathrm{~cm}) \times(18 \mathrm{~cm}) \times(5 \mathrm{~cm})}{25}=(4 \mathrm{~cm}) \times(18 \mathrm{~cm}) \times(1 \mathrm{~cm})=72 \mathrm{~cm}^{3}$.

Since the density of the loaf is $2 \mathrm{~g} / \mathrm{cm}^{3}$, then the mass of each piece is volume times density, or $\left(2 \mathrm{~g} / \mathrm{cm}^{3}\right) \times\left(72 \mathrm{~cm}^{3}\right)=144 \mathrm{~g}$.

Answer: (D)