Added utils for calculating price and unit cost

src/RaidGeld.sol

@@ -2,7 +2,7 @@
 pragma solidity ^0.8.13;
 
 import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
-import "@openzeppelin/contracts/access/Ownable.sol";
+import "@openzeppelin/contracts/access/ownable.sol";
 
 struct Raider {
     uint16 level;

src/RaidGeldUtils.sol

@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.13;
+
+import {Army} from "../src/RaidGeld.sol" 
+
+library RaidGeldUtils {
+  function calculateUnitPrice(uint8 unit, uint16 units) internal pure returns (uint256) {
+    require(unit <= 3, "No matching unit found");
+    uint256 price = uint256(unit);
+    uint256 unitsAlready = uint256(units);
+
+    // Each level costs 15% more than previous
+    uint256 PERCENT_INCREASE = 115;
+    for (uint256 i = 0; i < n; i++) {
+        newPrice = newPrice * PERCENT_INCREASE / 100;
+    }
+    return unitBaseCost + (unitBaseCost * 15 / 100);
+  }
+
+  function calculateProfitsPerSecond(Army army) internal pure returns (uint256) {
+    // Each next unit scales progressivelly better
+    uint256 moloch_denier_profit = army.moloch_denier.level;
+    uint256 apprentice_profit = army.apprentice.level * 61 / 10;
+    uint256 annointed_profit = army.annointed.level * 6 * 64 / 10;
+    uint256 champion_profit = army.champion.level * 61 / 10 * 64 / 10 * 67 / 10;
+    return moloch_denier_profit + apprentice_profit + annointed_profit + champion_profit;
+  }
+}