How to calculate the rapid interpolation method The cost of 1 million is 78 million, and the cost of 30 million is 78 million. How much is the cost of 2006 million?

How to calculate the rapid interpolation method The cost of 1 million is 78 million, and the cost of 30 million is 78 million. How much is the cost of 2006 million?

If the cost of 2006 is x, then:
(x-0.78)/(2006-100)=(7.8-x)/(3000-2006)
x=5.39383448