Concept: The question tests on Word Problem
Solution:
5 calls last 1 minute and 5 calls last 3 minutes. The total call time = (5 * 1) + (5 * 3) = 5 + 15 = 20 minutes
Total call cost = 20 * 0.25 = $5
Call card cost = 10 * 1 = $10
Total Cost = 10 + 5 = $15
Option C