I am finishing up my code and the last problem I haven't been able to solve is: when the final task for a lead is completed, I want the lead status to be updated. I have the task whoId field value, but I don't know how to use this value to access and update the lead that the task is related to. This is my code so far:

trigger Scheduler on Task (after insert, after update) {
    // Iterate through all tasks
    for(Task t : Trigger.new){
        // Schedule follow up task for completed tasks depending on task subjecct
        if(t.Status == 'Completed'){    
            if(t.Subject == 'Send Initial Email'){
                Task newTask = new Task(Subject = 'Make Initial Phone Call', IsReminderSet = True, ReminderDateTime = System.now()+1, Activitydate = System.now().date().addDays(1), WhoId = t.WhoId, ownerId = t.ownerId);
                insert newTask;
            } else if(t.Subject == 'Make Initial Phone Call'){
                Task newTask = new Task(Subject = 'Send Email #2', IsReminderSet = True, ReminderDateTime = System.now(), Activitydate = System.now().date(), WhoId = t.WhoId, ownerId = t.ownerId);
                insert newTask;
            } else if(t.Subject == 'Send Email #2'){
                Task newTask = new Task(Subject = 'Make Phone Call #2', IsReminderSet = True, ReminderDateTime = System.now(), Activitydate = System.now().date().addDays(1), WhoId = t.WhoId, ownerId = t.ownerId);
                insert newTask;
            } else if(t.Subject == 'Make Phone Call #2'){
                Task newTask = new Task(Subject = 'Send Email #3', IsReminderSet = True, ReminderDateTime = System.now(), Activitydate = System.now().date(), WhoId = t.WhoId, ownerId = t.ownerId);
                insert newTask;
            } else if(t.Subject == 'Send Email #3'){
                Task newTask = new Task(Subject = 'Make Phone Call #3', IsReminderSet = True, ReminderDateTime = System.now(), Activitydate = System.now().date().addDays(1), WhoId = t.WhoId, ownerId = t.ownerId);
                insert newTask;
            // When final task is completed, change lead status to 'unresponsive'
            } else if(t.Subject == 'Make Phone Call #3'){
                
                Lead myLead = [SELECT Id, Status FROM Lead WHERE Id = :t.whoId];       
                
                myLead.Status = 'Unresponsive';
                
                update myLead;
            }
        }    
    }
}

Any help would be greatly appreciated. Thank you!