(3)
(∃yM(y)&∃zP(z)) & ∀x(M(x) → P (x)),
(∃yS (y)&∃zM (z)) & ∀x(S(x) → M (x))
(∃yS(y)&∃zP(z)) & ∀x(S(x) → P (x)).
(4) ∀x(M(x) → P (x)), ∀x(S(x) → M(x)) ∀x(S(x) → P (x)).
∀x(S(x) → M(x))
∀
S(x) → M(x)[S(x)](5)
∀x(M(x) → P (x))
∀
M(x) → P (x)M(x)
P (x)
S(x) → P (x)
∀x(S(x) → P (x))
∀