Daniel used the formula to find the area of the following special trapezoid. His work is shown. Identify his error and correct it to find the area of the special trapezoid. \(\text{Line}\ 1:\ A=\frac{1}{2}\left(6\right)\left(7+ 7\right)\) \(\text{Line}\ 2:\ A=\frac{1}{2}\left(6\right)\left(14 \right)\) \(\text{Line}\ 3:\ A=\left(3\right)\left(7\right)\) \(\text{Line}\ 4:\ A=21\text{ cm}^2\)