This was a little confusing to read at times but I will bite on and try.
Answer:
dAJbUPm0rhsVWs854imUncz989e7MJ6M96tKKE5ysCY5ipnJx178LDJjHamSZWsTRWZGzrqZMOn3m4UDXDEImqACg3C2AAENBnp047jfsp9/8hdgk7v3Cm9oX0/DAWrjC0uYIIUroIOS/ArEMVkL6D5cdOOAofaayHuqc8DKk/w=
Now for some suggestions, its a little confusing that you introduce caesar cipher before you introduce what a substitution cipher is and may be better to reverse the two. Another thing, when coming down to the problem, is it was almost difficult to dissociate the problem from other text, your formatting is pretty good but with how you keep it like that its almost... It could be better.
Welcome to Steemit though!
RE: Cryptography Lesson1 Challenge 1