Define categories

Good day. I need to define the grade of employees for insurances plan. Column A is the grade code and column B is the grade name.

I need in column C, where grade code 1 & 2 = Plan A, grade code 3 = Plan B, and rest 4 to 9 = is Plan C {Where grade code 10 to 12 = empty}

Thank you in advance,

Regards,