Write all possible products of the base-catalyzed crossed aldol reactions between each pair of reaction partners given below. (Multiple products are possible in every case; be sure to include thermo-dynamically unfavorable as well as favorable ones.) 

(a) Butanal and acetaldehyde 

(b) 2,2-Dimethylpropanal and acetophenone 

(c) Benzaldehyde and 2-butanone