I'm confused where to really start with this question. Could someone steer me in the right direction? The prof doesn't really give examples, I think one or two in about 21 lectures and didn't mention where this was in the book.

Let F be the relation that contains the pair (a,b) if a and b are airports such that there is a direct non-stop airline

flight from a to b.

Further let T be the relation that contains the pair (a,b) if a and b are stations such that there is a direct train

connection from a to b.

(Assume that airports can also be stations.)

Produce English descriptions as answers to the following questions:

a) When is (a, b)E F^3?

b) When is (a, b)E F^*?

c) When is (a, b)E T ; F ; T?

d) When is (a, b)E (F ; T) U T?

e) When is (a, b)E (F ; T) - T^*?