Find the Largest Open Intervals Where the Function Is Concave $f(x)=4 x^{3}-45 x^{2}+150 x$

Multiple Choice

Find the largest open intervals where the function is concave upward.
- $f(x) =4 x^{3}-45 x^{2}+150 x$

A) $\left(-\frac{15}{4}, \infty\right)$
B) $\left(\frac{15}{4}, \infty\right)$
C) $\left(-\infty,-\frac{15}{4}\right)$
D) $\left(-\infty, \frac{15}{4}\right)$