text: module.exports = {
    add: function(a, b) {
      return a + b;
    },
    subtract: function(a, b) {
      return a - b;
    },
    divide: function(a, b) {
      if(b == 0 ) {
        throw new Error('divide by zero')
      } else {
        return a / b;
      }
    }
  }