Python pycharm

B = (3.5, 3.7, 5.0, 10.6, 25.3, 50.6)

1. What is wrong with: B[3] = 10.6 ?
2. Write output for:

print('Slice sum = {mySum:06.2f}'.format(mySum=sum(B[-3:1:-1])))

3. Write an equivalent line of code to the above print statement using all positive numbers for slicing.
4. Is a, b, c = B[-1:-5:-1] allowed?
5. If d. is allowed, what is the value of b? If d. is not allowed, correct the statement (by changing only one character) and tell the value of b.