Differentiate. $(2$ marks $)$

f$($x$)=(3$x$-2)(3$x $+1)$

f$\text{'}($x$)=18$x$-1\mathrm{.}5$

f$\text{'}($x$)=18$x$-9$

f$\text{'}($x$)=9$x$-3$

f$\text{'}($x$)=18$x$-3$