Answer: work done = 14478ft²-lb/s²
Step-by-step explanation: The work done is equal to the rest energy of the chain.
The rest energy is also the potential energy Mass* hieght*acceleration due to gravity.
But in this case we have to look for our acceleration due to gravity in ft/s².
I googled it an I got 32.174ft/s²
So now let's substitute
Work done = m*g*h
= 45*32.174*10=14478ft²lb/s².