The marketing department of a popular electronic store is preparing its work plan for the next financial year. The manager is seeking a 20% increase in advertising budget. He used the simple linear regression technique to analyse the past 10 years' sales and advertising data and noted these results:

• Correlation = 0.86
• For every $1 spent on advertising, the impact is a $5 increase in sales

The manager received approval for the increased advertising budget and rolled out a series of advertising campaigns for the store. Discuss whether the manager's approach is valid. Justify your point of view.