Life Insurance coverage - Salary + fixed amount

Hi

My client has a requirement of creating Basic Life Insurance Plan that is based on employees' base salary. This is divided into 3 classes with following coverage amount.

In Class1 ( Base < $ 25K ) = 1 x base puls 30K

Class2 ( Base = 25 K to $ 150000) = 1 x base plus 50K

Class 3 ( Base = 150001 and over) = 1 x base upto 1M

My understanding is that system can calculate the coverage amount as any multiple of bases salary, but how can we add a flat amount to it so that coverage amount becomes 1 x Base plus a flat amount.

Any help is appreciated.

Thanks

W