Question 19
The diagram below on the left shows the closed window of an old bus. All curves forming the round corners are arcs of a quarter circle with radius 13 cm. The two sliding windows on top have equal size and their height is 15 cm. To open the window, the upper parts of the bus window are slid left or right, as shown in the diagram below on the right. If the left window is slid 10 cm to the right, and the right window is slid 8 cm to the left, what is the total area, in cm$^2$, of the opening (the total shaded area)? (Take $\pi=3.14$.)
