To find d , the diagonal through the box, which would be the best idea to use?

Question

a
Find d, the diagonal of the box, using the Pythagorean Theorem with sides 20 and 6. Then, use the Pythagorean Theorem again with sides d and 6 to solve for s.

b
Find s, the diagonal of the bottom of the box, using the Pythagorean Theorem with sides 6 and 6. Then, use the Pythagorean Theorem again with sides s and 20 to solve for d.

c
Find s, the diagonal of the bottom of the box, using the Interior Angle Theorem with sides 20 and 6. Then, use the Interior Angle Theorem again with sides s and 6 to solve for d.

d
Find s, the diagonal of the bottom of the box, using the Pythagorean Theorem with sides 20 and 6. Then, use the Pythagorean Theorem again with sides s and 6 to solve for d.