Under certain conditions, when (R)-2-bromobutane is heated with water, the SN1 substitution proceeds twice as fast as

Question:

Under certain conditions, when (R)-2-bromobutane is heated with water, the SN1 substitution proceeds twice as fast as the SN2 Calculate the e.e. and the specific rotation expected for the product. The specific rotation of (R)-butan-2-ol is - 13.5(. Assume that the SN1 gives equal amounts of the two enantiomers.