/**
 * This function takes the fuel cost, maintenance cost, and flight hours as inputs
 * and calculates the total variable cost for an aerospace engineer.
 */
fun calculateVariableCost(fuelCost: Double, maintenanceCost: Double, flightHours: Int): String {

    if (fuelCost >= 0 && maintenanceCost >= 0 && flightHours >= 0) {
        // Calculate the total variable cost by multiplying fuelCost and flightHours, and add maintenanceCost
        val totalVariableCost = fuelCost * flightHours + maintenanceCost
        return "The total variable cost is $${"%.2f".format(totalVariableCost)}."
    } else {
        return "Invalid input. All values must be non-negative."
    }
}
/**
 * This function takes the fuel cost, maintenance cost, and flight hours as inputs
 * and calculates the total variable cost for an aerospace engineer.
 */
fun calculateVariableCost(fuelCost: Double, maintenanceCost: Double, flightHours: Int): String {
/**
 * This function takes the fuel cost, maintenance cost, and flight hours as inputs
 * and calculates the total variable cost for an aerospace engineer.
 */
fun calculateVariableCost(fuelCost: Double, maintenanceCost: Double, flightHours: Int): String {

    if (fuelCost >= 0 && maintenanceCost >= 0 && flightHours >= 0) {
        // Calculate the total variable cost by multiplying fuelCost and flightHours, and add maintenanceCost
        val totalVariableCost = fuelCost * flightHours + maintenanceCost
        return "The total variable cost is $${"%.2f".format(totalVariableCost)}."
    } else {
        return "Invalid input. All values must be non-negative."
    }
}