Tanya has a garden with a trench around it. The garden is a rectangle with length 212m2 \dfrac12 \text{m} 2 2 1 m 2, start fraction, 1, divided by, 2, end fraction, start text, m, end text and width 2 m2 \text{ m} 2 m 2, start text, space, m, end text . The trench and garden together make a rectangle with length 312m3 \dfrac12 \text{m} 3 2 1 m 3, start fraction, 1, divided by, 2, end fraction, start text, m, end text and width 3 m3 \text{ m} 3 m 3, start text, space, m, end text . Find the area of just the trench.