Subject: mathqa
Question: each machine of type a has 3 steel parts and 3 chrome parts . each machine of type b has 6 steel parts and 5 chrome parts . if a certain group of type a and type b machines has a total of 60 steel parts and 44 chrome parts , how many machines are in the group
Option: 
A: 13
B: 12
C: 14
D: 15
Answer: C