C. Memory Buttons Click
a. Have one class level variable to hold the memory value
b. Memory add click, check to see that the math result display label has a value. If it has a value, add that value to the class level variable.
c. Memory subtract click, check to see that the math result display label has a value. If it has a value, add that value to the class level variable.
d. Memory Recall click, display the value in the memory variable in the memory display label
e. Memory Clear Click will set the memory variable value to 0 and clear the memory display label.