We first calculate the present value of cash flows as follows,

$P = \frac{80}{1.06^1} + \frac{80}{1.06^2} + \frac{1080}{1.06^3} = 1,053.46$

Thus, the Macaulay duration is given by,

$\text{Macaulay Duration} = \sum_{i=1}^{n} t_i \left[ \frac{PV(C_t)}{\sum PV(C_t)} \right]$

$= \frac{\frac{80}{1.06^1}}{1,053.46} \times 1 + \frac{\frac{80}{1.06^2}}{1,053.46} \times 2 + \frac{\frac{1080}{1.06^3}}{1,053.46} \times 3$

$= 2.7891$