In what ratio mental A at Rs.68 per kg be mixed with another metal at Rs.96 per kg so that cost of alloy (mixture) is Rs.75 per kg?  Choose the correct choice from the following answers:
A) 5 : 8
B) 3 : 1
C) 3 : 7
D) 9 : 5
E) 9 : 8

Rationale: "( 96 - 75 ) / ( 75 - 68 ) = 21 / 7 = 3 / 1 answer : b"
Answer: B