Incur Credit Card Fees or Not?

Fees.scala

import squants.Dimensionless
import squants.DimensionlessConversions._
import squants.market._, MoneyConversions._

case class CreditCard(name: String, points: Dimensionless, checkingAPR: Dimensionless) {
  def charge(amount: Money, fee: Dimensionless = 0 percent, flatFee: Money = 0 dollars): String = {
    val fees = amount*fee + flatFee
    val interestEarned = amount * checkingAPR/12
    val cashBack = (amount + fees)*points
    val saved = cashBack - interestEarned - fees
    val (verdict, result) = if (saved < 0.dollars) {
      s"Too expensive to pay ${amount.toFormattedString} by $name card" -> "Pay in fees"
    } else {
      s"Use your $name card to pay ${amount.toFormattedString}" -> "Earn in points"
    }
    f"""
       |$verdict
       |Fees Charged             = ${fees.toFormattedString}%8s
       |Checking interest earned = ${interestEarned.toFormattedString}%8s
       |Cash back ($points)      = ${cashBack.toFormattedString}%8s
       |-------------------------------------------------------
       |${result.padTo(24, ' ')} = ${saved.abs.toFormattedString}%8s
    """.stripMargin
  }
}

/***********************************************************************************************/
val myCard = CreditCard(name = "Bank of America Premium Rewards", points = 1.5*1.75 percent, checkingAPR = 0.02 percent)
println(myCard.charge(amount = 5000 dollars, fee = 2.65 percent, flatFee = 2.25 dollars))