Task
Build the `Calc` class. Evaluate 7 expressions in sequence and print the history list.
Expressions: 2+3, 10*4, 100-1, 5**3, 7+7, 9*9, 100/4
After the loop, `print(list(calc.history))` should show only the last 5 (first two evicted):
Expected: [('100-1', 99), ('5**3', 125), ('7+7', 14), ('9*9', 81), ('100/4', 25.0)]