During a special study on learning, a psychologist found that, on the average, the rate of learning a list of special symbols in a code, N'(x), after x days of practice was given approximately by the table values below. Use left and right sums over 3 equal subintervals to approximate th area under the graph of N'(x) from x = 6 to x = 12. Calculate an error bound for this estimate. X N'(x) 0 30 2 25 4 6 8 22 16 15 10 12 12 10 The left sum, L3, is The right sum, R3, is The error bound is ...