Answer:
The discount rate is 13%
Explanation:
Step 1. Given information.
Step 2. Formulas needed to solve the exercise.
    g = return on equity * retention rate
    Stock price = dividend in next year/ (discount - g) Â
Step 3. Calculation.
 g = 15 * 0.2 = 3%
According to gordon growth model:
Stock price = dividend in next year/ (discount - g)
50 = 5/ (discount - g)
discount - g = 5/50
Discount - g = 10%
discount = 10 + 3 = 13%
Step 4. Solution.
The discount rate is 13%