For the function $f ( x ) = 4 x ^ { 3 } + x$, what is the value of $\lim _ { n \rightarrow \infty } \sum _ { k = 1 } ^ { n } \frac { 1 } { n } f \left( \frac { 2 k } { n } \right)$? [3 points] (1) 6 (2) 7 (3) 8 (4) 9 (5) 10
For the function $f ( x ) = 4 x ^ { 3 } + x$, what is the value of $\lim _ { n \rightarrow \infty } \sum _ { k = 1 } ^ { n } \frac { 1 } { n } f \left( \frac { 2 k } { n } \right)$? [3 points]\\
(1) 6\\
(2) 7\\
(3) 8\\
(4) 9\\
(5) 10