4 A camera shop stocks eight different types of batteries on

4. A camera shop stocks eight different types of batteries, one
of which is type A7b. Assume there are at least 30 batteries
of each type.
a. How many ways can a total inventory of 30 batteries be
distributed among the eight different types?
b. How many ways can a total inventory of 30 batteries be
distributed among the eight different types if the inventory
must include at least four A76 batteries?

c. How many ways can a total inventory of 30 batteries be
distributed among the eight different types if the inventory
includes at most three A7b batteries?

Solution