How to solve

A company is removing old metal pipes from its building and replacing them with plastic pipes, which will increase the usefulness of the building. The cost of installing the new plastic pipes is $90.$ The company only uses the Building account, and does not account for components such as Pipes separately.

You do not need to show any work$-$just the journal entries are sufficient.

a$.$ What is the appropriate journal entry when the company pays $90$ to replace the pies, if it can be assumed that the book value of the old pipes is NOT ZERO?

b$.$ What is the appropriate journal entry if it can be assumed that the book value of the old pipes is ZERO?