4. (5 points) As shown in the figure, a large square is divided into four identical rectangles and a small square. If the perimeter of one of the small rectangles is 28, then the area of the large square is $\qquad$ .


【Analysis】The perimeter of a small rectangle is 28, which means the sum of the length and width of the small rectangle is $28 \div 2=14$, which is also the side length of the large square. Then, according to the area formula of a square, solve the problem.

【Solution】Solution: $28 \div 2=14$
$$
14 \times 14=196
$$

Answer: The area of the large square is 196.
Therefore, the answer is: 196.