Chapter 2, Problem 2.14E

Given the equation $y=a{x}^3+7$, which of the following, if any, are correct C statements for this equation?
$\begin{array}{l}\text{a}\text{. } y=a*x*x*x+7;\\ \text{b}\text{.} y=a*x*x*\left(x+7\right);\\ \text{c}\text{.} y=\left(a*x\right)*x*\left(x+7\right);\\ \text{d}\text{.} y=\left(a*x\right)*x*x+7;\\ \text{e}\text{.} y=a*\left(x*x*x\right)+7;\\ \text{f}\text{. } y=a*x*(x*x+7;\end{array}$