Let $M, N$ be free modules over a Noetherian commutative ring $R$ and let $F$ be a field whose cardinality does not exceed the continuum. We prove the following: 1) The Injective Continuum Function Hypothesis, ICF, is equivalent to assertion that [ any two F-vector spaces are isomorphic iff their duals are so.] 2) If the dual of $M$ is a projective $R$-module and rank$_R(M)$ is infinite then the ring $R$ is Artinian. 3) If $R$ is Artinian and card$(R)$ does not exceed the continuum then the dual of $M$ is free. 4) If $M, N$ have isomorphic duals then they are themselves isomorphic (over $R$), when rank$_R(M)$ is not an $ω$-measurable cardinal and $R$ is a non-Artinian ring that is either Hilbert or countable. 5) If $R$ is a non-local domain then $R$ is a half-slender ring. We also prove that if the powersets of two given sets have equal cardinalities then there is a bijection from the one powerset to the other that preserves the symmetric difference of sets.