I design outdoor kitchens and most of my designs are straight islands or 90 degree "L" shapes so it's easy to find remaining measurements if you're only given a few. However, for three piece islands or soft (45 degree) "L" shapes I have no idea how to derive the remaining measurements if only the interior measurements are available. Usually you only know the interior measurements due to calculating the length required to accommodate the desired grill/equipment. But, it's better to know the exterior measurements for accurately pricing the kitchen. I've attached a picture illustrating what I'm after. Please math gurus, I've googled to no avail, you're my only hope!