What is the equation clearly showing the stereochemistry of the starting material and the product for the reaction of 2-bromobutane with sodium iodide in acetone?

2-bromobutane undergoes an SN2 reaction with sodium iodide in acetone, resulting in the substitution of the bromine atom with an iodine atom. The stereochemistry of the product is inversion of configuration, meaning the product is the opposite enantiomer of the starting material. The equation for this reaction can be represented as:

(R)-2-bromobutane + NaI → (S)-2-iodobutane + NaBr