Which of the following is the inverse of the relation {(1, 5), (2, 6), (1, 7), (4, 8)}?

a.
{(1, 5), (2, 6), (7, 1), (8, 4)}

b.
{(5, 1), (6, 2), (7, 1), (8, 4)}

c.
{(2, 6), (1, 5), (8, 4), (7, 1)}

d.
{(1, 7), (1, 5), (2, 6), (8, 4)}