Note that if the display window is resized, your Ying-Yang symbol must scale accordingly.

3. (15pt)  [Simple Calculator, Part III] Add event handling such that arithmetic operations work properly. You may leave decimal point, sign, backspace, and all the functions out for now. Note that since we are working on a "simple" calculator (as oppose to a "scientific" one), we will consider the operators all have the same precedence. For example, 1+2*3 will yield 9 instead of 7. A simplified version of the program is available here for your reference.