What is the basic idea of mobile telephony? What is the frequency range used in the operation of mobile phones?

Mobile phone acts in the frequency limit of

Signals of mobile phone are

A mobile phone charger is

______ is used for making mobile phones.

Cellular Mobile radio works on the frequency range is

The bar chart given below shows the sales (in '000 units) of 4 mobile brands for 3 years. What is the percentage increase in the number of mobile phones of Brand 2 sold from 2014 to 2015?