It was a monumental task: to design the world's tallest building, create as much usable rental space as possible, plan so it could be built within 18 months, and still have a handsome building. In the end, architect William Lamb worked on fifteen designs before his plan "K" was finally chosen. —The Building of Manhattan,
Donald A. Mackay

Which sentence is a summary of the central idea of the passage?

The design of the Empire State Building was difficult because it had to meet many criteria.
Architect William Lamb designed the building fifteen times before his plan was accepted.
The Empire State Building was the world’s tallest building.
The design for the Empire State Building was known as plan “K.”