$1\mathrm{.}51$n a recent biodiversity project, researchers deployed drones to capture aerial images ofa forest reserve. They aim to use automated image segmentation algorithms to identify and segment various landforms, such as water bodies, green patches, and rocky terrains.To evaluate the model's accuracy, a reference mask was manually created for a specific image.For a specific region of interest, the segmented output from the model delineates a water body in the shape of a rectangle. However, the manually curated reference mask shows a slightly different shape. To compare the two, the segmented area from the model is $1500$ sq$.$ and the area from the reference mask is $1800$ sq$.$ units. The overlapping region between the model's segmentation and the reference mask is $1200$ sq$.$ units. Based on the provided values, calculate the Intersection over Union $($loU$)$ for the segmented water body region to evaluate the accuracy of the model's segmentation against the reference mask.