The sum of first four terms of the G.P. 2, 6, 18, ………, is :

1. 26

2. 80

3. 160

4. 52

The sum of 20 terms of the G.P. 10, 20, 40, …… is :

1. 10(2¹⁹ - 1)

2. 10(2²¹ - 1)

3. 10(2²⁰ - 1)

4. none of these