-60312.2.


Do a quadratic fit to the function a+bx+cx^2 to get something that passes through the three data points and extrapolate back to the number given. [The fit happens to be -37526.3 + 11.3249 x - 0.000560744 x^2].

Of course this isn't right . Do you have more data points? And, you're certain there is a connection?