In what ratio must a grocer mix two varieties of pulses costing Rs. 15 and Rs. 20 per kg respectively so as to get a mixture worth Rs. 16.50 kg?
Choose the correct choice from the following choices:
A) 7 : 3  B) 3 : 7  C) 4 : 6  D) 5 : 7  E) 8 : 9

Rationale: "required rate = 3.50 : 1.50 = 7 : 3 . answer a"
Answer: A