func: function sendMinersToPlanet(uint numMiners) public payable {
      require(msg.value >= numMiners * PRICE_TO_MINE, "Not enough paid");
      require(planetPopulation < PLANET_CAPACITY, "Planet is full");
      mint(msg.sender, numMiners);
      for (uint i = 0; i < numMiners; i++) {
        sendSingleMinerToPlanet(msg.sender);
      }
    }