Calculate the indicated Riemann sum Upper S Subscript nSn​, for the function ​f(x)equals=x squared minus 7 x minus 8x2−7x−8. Partition left bracket 1 comma 7 right bracket[1,7] into six subintervals of equal​ length, and let c1=1​, c2=3​, c3=3​, c4s=5​, c5=5​, and c6=7.