State one feature of the measurements that supports using a linear model for $V$

Using the measurements at $t=0$ and $t=6$ determine the gradient $m$ and intercept $c$ of the linear model $V(t)=mt+c$ Hence write down the model.

Use your model to estimate the volume at $t=5$ minutes, giving your answer to the nearest $0.1$ litre. State whether this prediction involves extrapolation, giving a reason.