Answer:
Combined.
Step-by-step explanation:
Variation are generally of 4 types,
Direct Variation- When one of the variables increases or decreases, the other one increases or decreases.
Inverse Variation- When one of the variables increases, the other one decreases and vice versa.
Joint Variation- Where more than two variables are related directly
.
Combined Variation- A combination of direct or joint variation, and indirect variation.
So in this case, r is in combined variation with s and t. r is in direct variation with s and inverse variation with t. And c is the proportionality constant.
