Заполни пропуски

Дано: \(A\_1C\_1\parallel A\_2C\_2\parallel A\_3C\_3\) ; \(BA\_1=A\_1A\_2=A\_2A\_3\) ; \(BC\_3=12\) см.

\(BC\_1=\) [ ] см; \(C\_1C\_2=\) [ ] см; \(C\_1C\_3=\) [ ] см.