Select all the variable switches that are allowed. Consider each possible answer in isolation; the changes are not cumulative, unless stated. (Hint: there are 3 correct answers.)
Ey(Aw(R(y,w)->EzS(y,z,w))&ExR(x,y))
a. w to y
b. z to w
c. y to u
d. z to u, then w to z
e. w to x
f. w to z
