Let's start by learning about indexing. Indexing allows us to access the ith element in a sequence. For example,

if we have the list lst = [`a', `b', `c', `d'] and we want to access the `b' we can ask for lst[1]. Notice

that Python indexes from 0. This means if we want the rst element in a sequence we have to ask for seq[0].

If the rst element is at 0, in our list lst what index is the last element? How could we write a loop that

would look at every element?

Part A - Adding

Write a function add(numbers) that returns the sum of every second number in a given list. (E.g. calling

add([2,-3,5,8,10,1]) returns 6 because jQuery22406987211055221731_1585648880324??3 + 8 + 1 = 6.)

Part B - Flipping

Write a function flip(binary string) that takes a binary string (a string containing only 1s and 0s) and

returns a new string where every bit has been

ipped. (E.g. calling flip('001011') returns '110100'.)