On linear extension operators from growths of compactifications of products

We obtain some results on product spaces. Among them we prove that for noncompact spaces X1 and X2, the norm of every linear extension operator from C(β(X1 × X2) β (X1 × X2)) into C(β(X1 × X2)) is greater or equal than 2, and also that β(X1 × X2)β(X1 × X2) is not a neighborhood retract of β(X1 × X2).