From Mechanics

Here we use

\displaystyle \mathbf{r}=\mathbf{u}t+\frac{1}{2}\mathbf{a}{{t}^{\ 2}}+{{\mathbf{r}}_{0}}

According to the text

\displaystyle \mathbf{u}=\mathbf{i}+2\mathbf{j}

and part a) gave

\displaystyle \mathbf{a}=0\textrm{.}5\mathbf{i}-\mathbf{j}

We assume the starting point is the origin so that \displaystyle {{\mathbf{r}}_{0}}=0.

At \displaystyle t=10+40=50 we obtain

\displaystyle \mathbf{r}=(\mathbf{i}+2\mathbf{j}) \times 50+\frac{1}{2}(\mathbf{a}=0\textrm{.}5\mathbf{i}-\mathbf{j} )\times{{50}^{\ 2}}

The distance is the magnitude of this vector