Given the task definition and input, reply with output. In this task, you need to provide the correct option for a given problem from the provided options.

Problem: in what ratio must tea at rs . 62 per kg be mixed with tea at rs . 72 per kg so that the mixture must be worth rs . 64.50 per kg ? 
Options: a ) 3 : 1 , b ) 2 : 1 , c ) 5 : 2 , d ) 3 : 2 , e ) 3 : 4

a