#include <stdio.h>
#include <math.h> 

void polinomial(double a, double b, double c, double * x1, double * x2) {
	double bSqrMns4ac;
	printf("{a, b, c} = {%f, %f, %f}\n", a, b, c);
	bSqrMns4ac = pow(b, 2) - 4 * a * c;
	printf("bSqrMns4ac = %f\n", bSqrMns4ac);
	if (bSqrMns4ac < 0) {
		*x1 = 0;
		*x2 = 0;
	} else {
		*x1 = (-b - sqrt(bSqrMns4ac))/ (2 * a);
		*x2 = (-b + sqrt(bSqrMns4ac))/ (2 * a);
		printf("{x1, x2} = {%f, %f}\n", (-b - sqrt(bSqrMns4ac))/ (2 * a), (-b + sqrt(bSqrMns4ac))/ (2 * a));
	}
}

int main (void) {
	double beta1 = -1.88138742; // beta1: price coefficient
	double beta2 = 0.07182447; // beta2: price^2 coefficient; Note that beta2 is a in the polinomial.
	double beta3 = 0.30941525; // beta3: coefficient of MSC labelling effect on wild salmon
	double beta4 = 0.70772077; // beta4: coefficient of AB labelling effect on farmed cod
	double beta5 = 0.69330401; // beta5: coefficient of AB labelling effect on farmed salmon
	double betaLabel[3] = {beta3, beta4, beta5}; // We have three c for the polinomial; each labelling effect coefficient reflects a c.
	int priceStar = 8;
	double b;
	double wtpMSC[2], wtpABCod[2], wtpABSalmon[2];
	
	printf("\nbeta1 = %f, \nbeta2 = %f, \nbeta3 = %f (%f), \nbeta4 = %f (%f), \nbeta5 = %f (%f)\n\n", beta1, beta2, beta3, betaLabel[0], beta4, betaLabel[1], beta5, betaLabel[2]);
	
	b = 2 * beta2 * priceStar + beta1;	
	polinomial(beta2, b, betaLabel[0], & wtpMSC[0], & wtpMSC[1]);
	printf("WTP(MSC) = %f, %f\n\n", wtpMSC[0], wtpMSC[1]);
	
	polinomial(beta2, b, betaLabel[1], & wtpABCod[0], & wtpABCod[1]);
	printf("WTP(AB on cod) = %f, %f\n\n", wtpABCod[0], wtpABCod[1]);
	
	polinomial(beta2, b, betaLabel[2], & wtpABSalmon[0], & wtpABSalmon[1]);
	printf("WTP(AB on salmon) = %f, %f\n\n", wtpABSalmon[0], wtpABSalmon[1]);
	
	return 0;
}