Question 151Which is a set of factors of $(r-s)^{3}+(s-t)^{3}+(t-r)^{3}$ ?$\{r-s, s-t, t-r\}$$\{3 r-3 s, s+t, t+r\}$$\{r-s, s-t, t-2 r t+r\}$$\left\{r^{2}-s^{2}, s-t, t-r\right\}$