1. What does the following code prints?

def simple_sum(a=1, b=2):
    return a + b
b = 3
print simple_sum(4)

a) 7
b) 6
c) 5

2. Replace the following elements: def, return, print, assert in the following script:

XXX fib(n=10):   series = [1 for i in range(n+1)]
   for i in range(3,n):
      series[i] = series[i-1] + series[i-2]
   XXXX series

XXXX fib(5) == 5
XXXX fib(6)

Bonus question: Is the function thoroughly tested? Think about what would happen with fib(2)? fib(-1)?