//This is my code.
data class PriceInfo (
    val ratePerTimeUnit: String,
    // ratePerMonth is ratePerTimeUnit*24*30
    val ratePerMonth: String,
    // ratePerYear is ratePerTimeUnit*24*365
    val ratePerYear: String,
}
//Ivo's comments
Does this really need to be optional? Yes for ECS we need to calculate it, but if we always calculate it, then we know that it will always be there, right?
We could even move the calculation into this data class, possibly in the constructor even -- as you need to supply the rateTimePerUnit anyway?
//Does he mean to write like this?
data class PriceInfo (
    val ratePerTimeUnit: String,
    // ratePerMonth is ratePerTimeUnit*24*30
    val ratePerMonth: String = String.format("%.2f",(Double.parseDouble(ratePerTimeUnit) * 24.0 * 30.0)),
    // ratePerYear is ratePerTimeUnit*24*365
    val ratePerYear: String = String.format("%.2f",(Double.parseDouble(ratePerTimeUnit) * 24.0 * 365.0))
}
//But how to write the code about create new PriceInfo
val PriceInfo = PriceInfo( 10.0, ?, ?)
//Or like this
data class PriceInfo (
    val ratePerTimeUnit: String
){
    val ratePerMonth: String = String.format("%.2f",(Double.parseDouble(ratePerTimeUnit) * 24.0 * 30.0))
    val ratePerYear: String = String.format("%.2f",(Double.parseDouble(ratePerTimeUnit) * 24.0 * 365.0))
}