Subject: mathqa
Question: because he ’ s taxed by his home planet , mork pays a tax rate of 40 % on his income , while mindy pays a rate of only 20 % on hers . if mindy earned 4 times as much as mork did , what was their combined tax rate ?
Option: 
A: 30 %
B: 20 %
C: 24 %
D: 22.5 %
Answer: C