Incorrect Answer.
Incorrect Answer.
x ( 
y F(x, y)
y M(x, M(y)))
is not a meaningful formula in predicate logic. The "subformula"
M(y) serves as an argument to the predicate M in M(x, M(y)). This is not allowed
as arguments to predicates have to be terms. Inspect the
definition of predicate logic formulas in Chapter 2 for details.