Tea and Coffee are perfect substitute of each other, given the price of Tea and Coffee being `100 and `200 per Kg. a consumer is prepared to buy 3 Kg. of each. If the price of tea remain same and the price of Coffee rises to `400 per kg. the demand for Tea goes to 6 Kg. and that of Coffee falls to 1Kg. The elasticity of substitution between Tea and Coffee is

• A. 1
• B. 4
• C. 5
• D. 3