setExchangeRate basic logic structure

contracts/logics/settle/eth/exchangeRate.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.6.8;
+
+import { DSMath } from "../../../libs/safeMath.sol";
+
+contract LogicOne {
+
+    address poolToken;
+
+    function setExchangeRate() public {
+        // run setExchangeRate in address(this)
+    }
+
+    constructor (address ethPool) public {
+        poolToken = address(ethPool);
+    }
+
+    receive() external payable {}
+
+}