How many disk operations are needed to fetch the i-node for afile with the path name /usr/ast/courses/os/handout.t?

Question:

How many disk operations are needed to fetch the i-node for afile with the path name /usr/ast/courses/os/handout.t? Assume that the i-node for the root directory is in memory, but nothing else along the path is in memory. Also assume that all directories fit in one disk block.