Plot area from its sides

Area of a four-sided plot from its side lengths (the sides need not form a rectangle). Pass side_a, side_b, side_c, side_d in METRES going around the plot (A = front); if the user gives feet, convert first (1 ft = 0.3048 m) and say so. Four sides alone do not fix the shape: without a diagonal the answer is the LARGEST area those sides can enclose (the real plot can only be smaller), so say that and ask for one diagonal. With diagonal (corner where D meets A to corner where B meets C, metres) the exact area is returned (area_method "diagonal"). Optionally road_facing_sides (e.g. ["A"] or ["A","B"]) to detect a corner plot. Returns the area in sq.m, sq.ft and cents. Use for "my plot is 40x60x42x58 feet, what is the real area", "area of my irregular plot". Free.