code: function randomPrice(oldPrice, volatility) {
    const rnd = randomNumber();
    let changePercent = 2 * volatility * rnd;
    if (changePercent > volatility) {
      changePercent -= (2 * volatility);
    }
    const changeAmount = oldPrice * changePercent;
    const newPrice = oldPrice + changeAmount;
    return newPrice;
  }
docs: Return a random price based on the previous price and volatility
  @param {Number} oldPrice - the previous price
  @param {Number} volatility - the current volatility
  @return {Number} newPrice