A construction crew is building a rectangular foundation for a storage unit using solid concrete blocks, each measuring 1 foot by 1 foot by 1 foot. The foundation is designed to be 15 feet long, 12 feet wide, and 6 feet high. The interior space of the foundation (where the storage unit will sit) has walls and a floor that are each 1 foot thick. How many concrete blocks are used to build this foundation? Refer to the diagrams:
(Top View)

(Side View).