text: function solve(r){
      if (typeof(r) == 'number'){
          let area = r ** 2 * Math.PI;
          console.log(area.toFixed(2));
      } else {
          console.log(`We can not calculate the circle area, because we receive a ${typeof(r)}.`);
      }
  
  }
  
  solve(5)
  solve()