Tea and Coffee are perfect substitute of each other, given the price of Tea and Coffee being Rs. 100 and Rs. 200 per kg. a consumer is prepared to buy 3 kg. of each.
If the price of tea remains the same and the price of coffee rises to Rs. 400 per kg. the demand for tea goes to 6 kg and that of coffee falls to 1 kg. The elasticity of substitution between Tea and Coffee is
a) 1
b) 4
c) 5
d) 3