You seem confused at things that ought not be confusing you. You will struggle more and more if you do not get past this.
You MUST learn to resort to "Basic Principles". This will allow you to decode and evaluate ANY string of cash values. If all you know is a bunch of formulas for regular cash flows, you are toast.
When I looked at this problem, I did not even consider the concept that has stumped you - that the payments change from 4000 to 3000. I just saw individual cash flows.
If i = 0.10, v = 1/1.10, then
Original PV = 60000 + 4000v + 3000v^2 + 3000v^3 + 3000v^4 - 60000v^4
I'm not sure what is wanted for "Uniform Annual Cost". It could be this:
Uniform PV = P + Pv + Pv^2 + Pv^3 + Pv^4 = Original PV, where P is the Uniform Annual Cost.
You book or teacher will have to tell you exactly what is meant.
Basic Principles!!! Trust me on this.