Consider an economy with a linear homogeneous Cobb-Douglas production function with two inputs-capital and labour. The share of capital and labour are, respectively. 1/3 and 2/3. The rates of growth of capital and labour are, respectively 6% and 3% per annum. If the rate of growth of output is 6% per annum, what is the rate of growth of output due to Total Factor Productivity (TFP)?