HELP ME ASAP PLS FOR THIS PROBLEM I GOT IT WRONG I WANT TO KNOW THE CORRECT ANSWER PLS for reviewing

The distance between parallel tangents of a reversed curve is 12 meters and the central angle is 11 degrees. If the radius of the common curve is 150 meters, find the length (2 decimals) of the long chord from P.C.to P.T. of the reverse curve. X need help here

Some of the statement regarding a steam engine are mentioned below. Mark the correct option as your answer.Mark the correct answer.

1. Stream engine is an external combustion engine

2. Heat is converted into work in a steam engine

3. Steam is useful in driving the piston

4. All of the above

Problem 1:
Alice is rearranging her library. She takes the innermost shelf and reverses the order of books. If you want to automate this process, which data structure would you prefer to do this and why? 

Problem 2:
There are two persons A and B. Both are maintaining two book shelves. A takes the first book (the book he kept for the first time in the shelf) from the shelf and reads it. B prefers to take the last book and reads. After reading a book, both A and B keep the book in a separate shelf. Write a Python program to implement this process. Identify the data structures and define the operations accordingly.