Investment A offers a fixed annual interest rate of $6\%,$ compounded annually for $15$ years. Investment B offers the same fixed annual interest rate of $6\%,$ compounded annually for $15$ years, but it also provides a one$-$time bonus of $3\%$ of the principal after $10$ years. Describe how the graph of the investment with the bonus $($Investment B$)$ differs from the graph of the investment without the bonus $($Investment A$)$ over the $15-$year period. Include any relevant calculations.