Let f(x)=2x^3 over the interval [ 1 , 2 ] . Find a formula for the Riemann sum obtained by dividing the interval [ 1 , 2 ] into n equal sub-intervals and using the right endpoint for each c_k. Then, take a limit of these sums as n to calculate the true area under the graph of f over [ 1 , 2 ] . Show and explain your work.