For which interval(s) is the function increasing and decreasing?

y=3x^3-16x+2

a. increasing for −2.31 < x < 2.31; decreasing for x < −2.31 and x > 2.31

b. increasing for x lesser than -4/3 and ; decreasing for

c. increasing for and ; decreasing for

d. increasing for ; decreasing for and