A coin is tossed twice. Calculate the probability of each of the following occurring, commenting briefly on the basis of your calculation:
i. A head on the first toss;
ii. A tail on the second toss, given that the first toss was a head;
iii. Two tails;
iv. A tail on the first toss and a head on the second;
v. A tail on the first and a head on the second, or a head on the first and a tail on the second;
vi. At least one head on the two tosses.