Citrate synthase, one of the enzymes in the series of enzyme-catalyzed reactions known as the Krebs cycle,

Question:

Citrate synthase, one of the enzymes in the series of enzyme-catalyzed reactions known as the Krebs cycle, catalyzes the synthesis of citric acid from oxaloacetic acid and acetyl-CoA. If the synthesis is carried out with acetyl-CoA that has radioactive carbon in the indicated position, the isomer shown here is obtained.

a. Which stereoisomer of citric acid is synthesized, R or S?
b. Why is the other stereoisomer not obtained?
c. If the acetyl-CoA used in the synthesis does not contain 14Cwill the product of the reaction be chiral or achiral?