01.Answer

val intAddition: Monoid[Int] = new:
  def combine(x: Int, y: Int) = x + y
  val empty = 0

val intMultiplication: Monoid[Int] = new:
  def combine(x: Int, y: Int) = x * y
  val empty = 1

val booleanOr: Monoid[Boolean] = new:
  def combine(x: Boolean, y: Boolean) = x || y
  val empty = false

val booleanAnd: Monoid[Boolean] = new:
  def combine(x: Boolean, y: Boolean) = x && y
  val empty = true