Which of the following Boolean algebraic equation(s) is/are CORRECT?

Consider 4-variable functions $f1, f2, f3, f4$ expressed in sum-of-minterms form as given below.

$f1 = \sum(0,2,3,5,7,8,11,13)$

$f2 = \sum(1,3,5,7,11,13,15)$

$f3 = \sum(0,1,4,11)$

$f4 = \sum(0,2,6,13)$

With respect to the circuit given above, which of the following options is/are CORRECT?

Consider a Boolean expression given by $F(X, Y, Z) = \Sigma(3,5,6,7)$.

Which of the following statements is/are CORRECT?

Consider a Boolean function f(w, x, y, z) such that 

f(w, 0, 0, z) = 1

f(1, x, 1, z) = x + z

f(w, 1, y, z) = wz + y

The number of literals in the minimal sum-of-products expression of f is ______