In the added column Grade, assign grades as follows :

if sal is in range 700 — 1500, Grade is 1 ;
if sal is in range 1500 — 2200, Grade is 2 ;
if sal is in range 2200 — 3000, Grade is 3 ;
if sal is in range 3000 — Grade is 4 ;

Add a constraint (NN-Grade) in table Empl that declares column Grade not null.

Modify the definition of column Grade. Increase its size to 2.

Drop the table Empl.