Area of a rectangle having vertices A, B, C, and D with position vectors \[-\widehat{i}+\frac{1}{2}\widehat{j}+4\widehat{k},\widehat{i}+\frac{1}{2}\widehat{j}+4\widehat{k},\widehat{i}-\frac{1}{2}\widehat{j}+4\widehat{k}\]and \[-\widehat{i}-\frac{1}{2}\widehat{j}+4\widehat{k}\] respectively is