What is the output when the following code executes?

def mystery(a, b):
    a = a * 2
    b = b + a
    print(a, b)

def main():
    x = 1
    y = 7
    mystery(x, y)
    print(x, y)
    z = x + y
    y = z / 2
    mystery(z, y)
    print(y, z)
main()