CIF (Certificado de Identificación Fiscal): This is the tax ID number for all companies. It consists of a letter followed by hyphen and 8 or 9 digits (example: B-12345678). The letter represents the type of entity. Verify that entered number is valid

fun isCifValid(cif: String) : Boolean {
  return (cif.length == 9 || cif.length == 10) && cif.startsWith("B-")
}