Union and Intersection using interval notation

Question

D and E are sets of real numbers defined as follows.

D={y|y<4}

E={y|y\ge 7}

D ∪ E =

D ∩ E =

Answer 1

D = (-infinity, 4)

E = (7,infinity)

the union is (-infinity, 4) U (7, infinity)

the intersection is empty

Answer 2

D∩E = {y | y<4 and y>7} = φ = empty set

D∪E = {y | y<4 or y>7} = set of points on the number line that are either less than 4 or equal to or greater than 7