A Set of Four Built-In Bookshelves in to Be Constructed $14$

Multiple Choice

A set of four built-in bookshelves in to be constructed in a room. The floor-to-ceiling clearance is 6 ft 1 in. Each shelf is 7 in. thick. An equal space is to be left between shelves. What space should there be between each shelf and the next? ( There is no shelf against the ceiling and no shelf on the floor. ) Please do not use the rules for calculating with measurements.

A) $14$ in.
B) $12$ in.
C) $11$ in.
D) $17$ in.
E) $9$ in.