Let f be the function defined by f(x) = x + x and divide the interval [-1, 2] into six subintervals of equal length. For each of the following choices of tags, write out the corresponding tagged partition 'P of [-1, 2] and find S(f. 'P). a) The left endpoint of each subinterval is the tag. b) The right endpoint of each subinterval is the tag. c) The midpoint of each subinterval is the tag. L definition of the Riemann integral is unique.