I am wondering if I can get help on the following problem:

If we have a stock of n batteries, each has a lifetime that is exponential

with parameter c and they are independent of each other.

If a flashlight needs 2 batteries, what is the lifetime that the flashlight can operate?

I have 2 solutions that I can think of:

1) The lifetime of the minimum (X,...Xn).

2) The lifetime of the min(Xi,Xj) multiply by all possible pairs, 2 choose n.

Any suggestion???