Answer:
The answer to your question is below
Explanation:
a) Yes, Joy can conclude that ΔABC is similar to ΔEDC because
∠ACB ≅ ∠ECD they are vertical angles and,
∠ABC ≅ ∠EDC they are right angles
We conclude that ΔABC is similar to ΔEDC because of the AA postulate.
b)

Solve for AB
AB = (BC)(DE) / (CD)
Substitution
AB = 105 (90) / 85
Simplification
AB = 105(1.06)
Result
AB = 111.2 ft