2024 AMC 8 Problem 3

Four squares of side length 4, 7, 9, and 10 units are arranged in increasing size order so that their left edges and bottom edges align. The squares alternate shaded and unshaded, as shown in the figure. What is the area of the visible shaded region in square units?

\textbf{(A)} 42 \qquad \textbf{(B)} 45 \qquad \textbf{(C)} 49 \qquad \textbf{(D)} 50 \qquad \textbf{(E)} 52

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.