A liquid is contained in a vertical tube of semicircular cross-section (figure). The contact angle is zero. The forces of surface tension on the curved part and on the flat part are in ratio:

1. \(1:1\)
2. \(1:2\)
3. \(\pi:2\)
4. \(2: \pi\)

Air is pushed carefully into a soap bubble of radius \(r\) to double its radius. If the surface tension of the soap solution is \(T,\) then work done in the process is: