Losey wrote

When translated into the Karnaugh map I got this:

s\ab

**00 01 11 10**

**0 ** 0 0 1 1

**1** 0 1 1 0

This is the correct k-map for Mux.

When I translated this into a formula I got this:

f (a,b,s) = AB + BS + AS (this last "S" with a line over it)

You can write Not(x) as ~x or !x when typing, as in

f (a,b,s) = AB + BS + A ~S

(I like to put a space before it as shown so that it stands out a bit.)

When simplifying using the k-map, you only need the minimum number of minterms (the rectangles of 1s) that produce the required 1s, so in this case the two minterms A ~S and BS are sufficient.

f (a,b,s) = BS + A ~S

The "+" is the Or function, so

f (a,b,s) = Or (And (B, S), And (A, Not (S)))

--Mark