Heat and Mass Transfer

An aqueous sucrose solution containing $18.0\text{ g}$ of sucrose (molecular weight $M_w = 342.3\text{ g/mol}$) dissolved in $100.0\text{ g}$ of pure water ($M_w = 18.015\text{ g/mol}$) behaves as an ideal dilute solution. Using Raoult's law ($a_w = x_w = \frac{n_w}{n_w + n_s}$), the water activity ($a_w$) of this solution is ________ (round off to three decimal places).