Approximate the double integral of f (x comma y )equals x plus y over the region r bounded above by the semicircle y equals startroot 16 minus x squared endroot and below by the x-axis, using the partitions x equals negative 4 comma negative 2 comma 0 comma 1 comma 2 comma 4 and y equals 0 comma 2 comma 4 with (x subscript k baseline comma y subscript k baseline )the lower left corner in the kth subrectangle (provided the subrectangle lies within r).