please help. 160+40+10+...=.... a.160 b.213 c.213 1/3 d.480 e.640

Deret tak hingga,
a = 160
r = 1/4
[tex]\displaystyle S_\infty=\frac{a}{1-r}=\frac{160}{1-\frac{1}{4}}=\frac{160}{^3/_4} \\ S_\infty=160\times \frac{4}{3}=\frac{640}{3}=213\frac{1}{3}[/tex]