Find the ratio in which rice at Rs.7.10 a kg be mixed with rice at Rs.5.70 a kg to produce a mixture worth Rs.6.30 a kg? Choose the most appropriate option:
A) 1 : 3
B) 2 : 3
C) 3 : 4
D) 4 : 5
E) none of these

Rationale: "solution required ratio = 60 : 80 = 3 : 4 answer c"
Answer: C