The weight in g, of the non-volatile solute urea $(NH_2CONH_2)$ to be dissolved in 100 g of water in order to decrease its vapour pressure by 1.8% is:

Question

$\begin {array} {1 1} (1)\;6.0 & \quad (2)\;0.3 \\ (3)\;3.0 & \quad (4)\;0.6 \end {array}$