Please show me the steps in solving this problem

15. An apartment complex has 1000 units of which on average 100 are vacant at any given time. Per unit, the rent is $400 per month, and the operating expenses are $1800 per year. If you expect both rents and expenses to grow at 3 percent per year, and the required return is 12.5 percent and the building value is expected to remain a constant multiple of its net income, then what is the NPV of a deal to buy the property for $25,000,000? [Hint: use the perpetuity formula: PV=CF₁/(r-g).]