To find out who spent more time writing per problem, we need to calculate the unit rate (minutes per problem) for Sonia and Maryna.
For Sonia:
- \( 6 \) problems in \( 120 \) minutes: \( \frac{120}{6} = 20 \) min/problem
- \( 18 \) problems in \( 360 \) minutes: \( \frac{360}{18} = 20 \) min/problem
- \( 25 \) problems in \( 500 \) minutes: \( \frac{500}{25} = 20 \) min/problem
- \( 60 \) problems in \( 1,200 \) minutes: \( \frac{1200}{60} = 20 \) min/problem
So, Sonia consistently spends 20 minutes per problem.
For Maryna:
- \( 8 \) problems in \( 200 \) minutes: \( \frac{200}{8} = 25 \) min/problem
- \( 15 \) problems in \( 375 \) minutes: \( \frac{375}{15} = 25 \) min/problem
- \( 20 \) problems in \( 500 \) minutes: \( \frac{500}{20} = 25 \) min/problem
- \( 50 \) problems in \( 1,250 \) minutes: \( \frac{1250}{50} = 25 \) min/problem
So, Maryna consistently spends 25 minutes per problem.
Conclusion: Maryna spent more time writing per problem at the unit rate of 25 min/problem. Therefore, the correct response is:
Maryna spent more time writing per problem at the unit rate of 25 min/problem.