Finding Subsets of $A$ that involves $a$ and $b$, not involves $f$

Question

$$A =\{a,b,c,e,d,f\} $$

• How do we find the subsets of $A$ that involves $a$ and $b$, not involves $f$?

I know that

$$\text {S} = 2^n$$

Regards

Answer 1

Hint: Think of all the subsets $B=\{c, d, e \}$.

Then union each with $\{a, b\}$.