hi i have written a code with multiple functions and i was wondering how i could multiply these functions together. a value is given to the functions from user input as seen below.

Code:
int main()
{
printf("-- Wind turbine power calculator -- \n");


getType();


getDiameter();


getAltitude();


getVelocity();


getPerformance();


getGenerator();


getGearbox();






return 0;
}
this is my main function in my code and i need to find this equation power = type x altitude x velocity x performance x generator x gearbox i was wondering how i could write a code that would perform this in order to calculate the power. the functions are written in this form

Code:
double getAltitude()
{
double a;


printf("\nEnter altitude (m):");
scanf("%lf", &a);


if (a > 9000)
{
printf("Invalid input! Altitude must be between 0 and 9000m");
return getAltitude();
}
else if ( a < 0 )
{
printf("Invalid input! Altitude must be between 0 and 9000m");
return getAltitude();
}
}
if this is not possible and i need to write the code in a different manner please let me know or if you have a solution then cheers.