Exercise B

Using the following symbolization key:

• domain:

  people

• $K(x)$:

  $\underline{\hskip 15.00002pt}_{x}$ knows the combination to the safe

• $S(x)$:

  $\underline{\hskip 15.00002pt}_{x}$ is a spy

• $V(x)$:

  $\underline{\hskip 15.00002pt}_{x}$ is a vegetarian

• $h$:

  Hofthor

• $i$:

  Ingmar

symbolize the following sentences in FOL:

1. Neither Hofthor nor Ingmar is a vegetarian.

2. No spy knows the combination to the safe.

3. No one knows the combination to the safe unless Ingmar does.

4. Hofthor is a spy, but no vegetarian is a spy.