The value (up to two decimal places) of a line integral $\int_C \overrightarrow{F}(\overrightarrow{r}) . d\overrightarrow{r}$, for $ \overrightarrow{F}(\overrightarrow{r}) = x^2 \hat{i} + y^2 \hat{j} $ along $C$ which is a straight line joining $(0, 0)$ to $(1, 1)$ is _____