To determine whether a stock is overvalued or undervalued, we need to compare the expected return (or holding period return) and the required return (from Capital Asset Pricing Model, or CAPM).

Step 1: Calculate Expected Return (Holding period return):

The formula for the (one-year) holding period return is:

HPR = (D₁ + S₁ – S₀) / S₀, where D = dividend and S = stock price.

Here, HPR = (0 + 55 – 45) / 45 = 22.2%

Step 2: Calculate Required Return:

The formula for the required return is from the CAPM:

RR = R_f + (ER_M – R_f) × Beta
RR = 4.25% + (12.5 – 4.25%) × 2.31 = 23.3%.

Step 3: Determine over/under valuation:

The required return is greater than the expected return, so the security is overvalued.
The amount = 23.3% − 22.2% = 1.1%.