Calculating disk accesses?

I have a test that I am retaking and cannot for the life of me find anything to help me answer this question.

Consider an ordered data file of 500,000 records stored on a disk with a usable block size of 8192 bytes. Each record has average length of 255 bytes, including an ordering key field of 6 bytes. A block pointer is 4 bytes long. 

a) Calculate the average number of disk accesses required for a binary search on a key value of the file 
Note – answers can be left in logarithmic notation. 
i) using a single-level primary index file 
ii) using a multi-level primary index file 
iii) without using any indexes 
iv) If the same file is unordered calculate the average number of disk accesses required for a search using a single-level and multi-level index

Thanks