We will have the following:
2. The graph showing each account's balance are:
The one that increases at a constant rate is represented by the "triangles".
The one that doubles each time is represented by the "circles"
You will determine it as follows: First of all a constant increase represents a linear growth [In other words the graph would be a straigh line], and the values that double each time represent an exponential growth, so It will start "slow" and then it will "spike" in an instant.
3.If given the choise you should pick the one that doubles each time. Each time the money will double and after a few weeks will have more money than the one that increases by a constant rate.