AWS Certified Solutions Architect - Professional (#527)

A customer has a website which shows all the deals available across the market. The site experiences a load of 5 large EC2 instances generally. However, a week before Thanksgiving vacation they encounter a load of almost 20 large instances. The load during that period varies over the day based on the office timings. Which of the below mentioned solutions is cost effective as well as help the website achieve better performance?

Setup to run 10 instances during the pre-vacation period and only scale up during the office time by launching 10 more instances using the AutoScaling schedule.
Keep only 10 instances running and manually launch 10 instances every day during office hours.
During the pre-vacation period setup 20 instances to run continuously.
During the pre-vacation period setup a scenario where the organization has 15 instances running and 5 instances to scale up and down using Auto Scaling based on the network I/O policy.