diff --git a/index.js b/index.js
index 3bb4d07..b75042b 100644
--- a/index.js
+++ b/index.js
@@ -4,7 +4,27 @@
  * Depending on the operation, either add up all of the numbers or subtract all of the numbers, from left to right.
  * @returns {number} The result of either adding all numbers or subtracting all numbers, depending on the arguments added to the command line.
  */
-function calculator() {}
+function calculator() {
+    if (!process.argv[2]) {
+        return (`No operation provided...`);
+    } else if (!process.argv[3]) {
+        return (`No numbers provided...`);
+    } else if (process.argv[2] != "plus" && process.argv[2] != "minus") {
+        return (`Invalid operation: ${process.argv[2]}`);
+    } else if (process.argv[2] === "plus") {
+        let number = 0;
+        for (let i = 3; i < process.argv.length; i++) {
+            number += Number(process.argv[i]);
+        }
+        return number;
+    } else if (process.argv[2] === "minus") {
+        let number = process.argv[3];
+        for (let i = 4; i < process.argv.length; i++) {
+            number -= Number(process.argv[i]);
+        }
+        return number;
+    }
+}
 
 // Don't change anything below this line.
 module.exports = calculator;
diff --git a/package-lock.json b/package-lock.json
index 99b1c39..4e41b08 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -5,6 +5,7 @@
   "requires": true,
   "packages": {
     "": {
+      "name": "8-0-javascript-on-your-machine-lab",
       "version": "1.0.0",
       "license": "ISC",
       "devDependencies": {
@@ -1307,14 +1308,20 @@
       }
     },
     "node_modules/caniuse-lite": {
-      "version": "1.0.30001241",
-      "resolved": "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001241.tgz",
-      "integrity": "sha512-1uoSZ1Pq1VpH0WerIMqwptXHNNGfdl7d1cJUFs80CwQ/lVzdhTvsFZCeNFslze7AjsQnb4C85tzclPa1VShbeQ==",
-      "dev": true,
-      "funding": {
-        "type": "opencollective",
-        "url": "https://opencollective.com/browserslist"
-      }
+      "version": "1.0.30001420",
+      "resolved": "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001420.tgz",
+      "integrity": "sha512-OnyeJ9ascFA9roEj72ok2Ikp7PHJTKubtEJIQ/VK3fdsS50q4KWy+Z5X0A1/GswEItKX0ctAp8n4SYDE7wTu6A==",
+      "dev": true,
+      "funding": [
+        {
+          "type": "opencollective",
+          "url": "https://opencollective.com/browserslist"
+        },
+        {
+          "type": "tidelift",
+          "url": "https://tidelift.com/funding/github/npm/caniuse-lite"
+        }
+      ]
     },
     "node_modules/chalk": {
       "version": "4.1.1",
@@ -4979,9 +4986,9 @@
       "dev": true
     },
     "caniuse-lite": {
-      "version": "1.0.30001241",
-      "resolved": "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001241.tgz",
-      "integrity": "sha512-1uoSZ1Pq1VpH0WerIMqwptXHNNGfdl7d1cJUFs80CwQ/lVzdhTvsFZCeNFslze7AjsQnb4C85tzclPa1VShbeQ==",
+      "version": "1.0.30001420",
+      "resolved": "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001420.tgz",
+      "integrity": "sha512-OnyeJ9ascFA9roEj72ok2Ikp7PHJTKubtEJIQ/VK3fdsS50q4KWy+Z5X0A1/GswEItKX0ctAp8n4SYDE7wTu6A==",
       "dev": true
     },
     "chalk": {