I cant get the correct output for this in kotlin

Question

fun shippingCost(amount: Double, international: Boolean): Double{
val amount: Double= readLine()!!
println("The amount is: $amount")
val international =true
val total: Double= when{
amount>=75.0&&international==false->amount
amount<75.0&&international==false->10/100*amount+amount
international==false->15/100*amount+amount
else-> 0.0
}
return (total)
}
fun main(args: Array<String>) {
val total = readLine()!!.toDouble()
val international = readLine()!!.toBoolean()
println(shippingCost(total, international))
}

Answer 1

What is the reason for lines 3,4&5?
Also, please double check that your conditions are matched with the given task.