$3\mathrm{.}4.$ Suppose that a data warehouse consists of the three dimensions time, doctor, and patient, and

the two measures count and charge, where charge is the fee that a doctor charges a patient for a

visit.

$($a$)$ Enumerate three classes of schemas that are popularly used for modeling data warehouses.

$($b$)$ Draw a schema diagram for the above data warehouse using one of the schema classes listed

in $($a$).$

$($c$)$ Starting with the base cuboid $[$day$,$ doctor,patient$],$ what specific OLAP operations should be

performed in order to list the total fee collected by each doctor in $2010?$

$($d$)$ To obtain the same list, write an SQL query assuming the data are stored in a relational

database with the schema fee $($day$,$ month, year, doctor, hospital, patient, count, charge$).$