Answer:
1/3
Explanation:
The probability of a student winning is 1/4.
The probability of a prize being selected is 1/3.
The probability of Gail winning a scarf is 1/4 × 1/3 = 1/12.
The probability of Simon winning is 1/4.
The probability of either is 1/12 + 1/4 = 1/3.