How to create multiple excel formula in one cell relative to data in another cell

Hello team

I have 2 excel tabs in one sheet (TAB A & TAB B)
one tab (TAB A) has the values already inserted.
another tab (TAB B) has the required calculations.

I have created a column in TAB B with a drop-down list relatable to values in a column from TAB A.
I want another cell in TAB B that will auto compute values dependent on each selection made off the drop-down list.
I believe IF and OR functions are applicable but i don't know where to start from. Thanks