Each R requires $6$ of component S; each S requires $4$ of part T$.$ The lead time for assembly of R is $2$ week. The lead time for the manufacture of S is $6$ weeks. The lead time for the procurement of T is $16$ weeks. The cumulative lead time for R is $\_\_\_\_\_\_\_\_\_\_$ weeks.

A$.16$

B$.18$

C$.28$

D$.12$

E$.9$