Hi, if a tenancy agreement is made for 5 years with a different rental amount for 2 years and a higher rental for the next 3 years, how can we calculate the stamping fees?

For example,
Month 1-24 = RM 1500
Month 25-60 = RM 4000

The guides I find online calculate the stamping duty based on one year of rental. How do we calculate when the yearly rental changes over the term of the agreement? Any clues?