Tanya has a garden with a trench around it. The garden is a rectangle with length212m221m2, start fraction, 1, divided by, 2, end fraction, start text, m, end text and width2m2 m2, start text, space, m, end text. The trench and garden together make a rectangle with length312m321m3, start fraction, 1, divided by, 2, end fraction, start text, m, end text and width3m3 m3, start text, space, m, end text. Find the area of just the trench.