@@ -0,0 +1,561 @@
+//@@author A0141052Y%0Apackage seedu.address.model;%0A%0Aimport seedu.address.model.task.ReadOnlyTask;%0A%0A/**%0A * Represents the preceding state of the current Model%0A */%0Apublic class ModelHistory %7B%0A    %0A    private ReadOnlyTask previousTask;%0A    %0A    /**%0A     * Initializes a ModelHistory with an empty history%0A     */%0A    public ModelHistory() %7B%0A        previousTask = null;%0A        %0A    %7D%0A    %0A    public ReadOnlyTask getPreviousTask() %7B%0A        return previousTask;%0A    %7D%0A    %0A    public void setPreviousTask(ReadOnlyTask task) %7B%0A        previousTask = task;%0A    %7D%0A%7D%0A

Add ModelHistory class to record state changes in Model