The $8$ gigabyte $(1$ GB $=23$ bytes$)$ flash memorychip for an MP$3$ player is $10$ mm by $20$ mm by $2$ mm$.$This memory chip holds $15,000$ photos.a$)$ How many photos fit into a cube whose sides are $2$ mm$?$b$)$ How many bytes of memory are stored in a cube whose sides are $100$ um$?$