#include<cmath>
using namespace std;

#define NLAYERS_BCAL 10
double BCAL_tdiff(double geometric_mean, int layer)
{
	double tw_par[NLAYERS_BCAL][7] ={
		{54.7858, -30.1543, 4.73011, 0.0923279, -0.0789792, 0.00514771, -3.22595e-05},	// layer 1
		{-1232.58, 1476.13, -721.447, 184.716, -26.1834, 1.95105, -0.0597667},	// layer 2
		{-2341.59, 1947.88, -480.606, -19.6095, 27.4221, -4.32381, 0.220259},	// layer 3
		{0, 0, 0, 0, 0, 0, 0},	// layer 4
		{0, 0, 0, 0, 0, 0, 0},	// layer 5
		{0, 0, 0, 0, 0, 0, 0},	// layer 6
		{0, 0, 0, 0, 0, 0, 0},	// layer 7
		{0, 0, 0, 0, 0, 0, 0},	// layer 8
		{0, 0, 0, 0, 0, 0, 0},	// layer 9
		{0, 0, 0, 0, 0, 0, 0}	// layer 10
		};

	layer = layer<1 ? 1:layer>NLAYERS_BCAL ? NLAYERS_BCAL:layer;
	double *p = tw_par[layer-1];
	double x = log(geometric_mean);
	return p[0]+x*(p[1]+x*(p[2]+x*(p[3]+x*(p[4]+x*(p[5]+x*p[6])))));
}