A thin transparent film with refractive index 1.4 is held on a circular ring of radius 1.8 cm. The fluid in the film evaporates such that transmission through the film at wavelength 560 nm goes to a minimum every 12 seconds. Assuming that the film is flat on its two sides, the rate of evaporation is:

What comes next in the series?
\(2, 6, 12, 20, 30, \ ?\)
In a sequence of numbers, each term is generated by multiplying the previous term by 2 and then subtracting 1. If the first term is 3, what is the fourth term in the sequence?
The following data shows the number of students in different streams in a school: 
Which type of graph is best suited to represent this data?