Identify the type of design being described in below scenario.
Rhonda is studying the effects of hunger on academic performance. She uses hunger as a within-subjects factor, starting her subjects out with a very small breakfast and testing them at two-hour intervals throughout the day without any additional meals or snacks. She has a between-subjects factor of task difficulty, with three levels: easy, medium, and hard.
Options:
a. Combined strategy
b. Higher-order factorial
c. Mixed design