diff --git a/index.js b/index.js
index 3bb4d07..8a57bf4 100644
--- a/index.js
+++ b/index.js
@@ -4,7 +4,29 @@
  * 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() {
+    let total = 0 
+    if (!process.argv[2]) {
+        return `No operation provided...`
+    }else if(!process.argv[3]){
+        return `No numbers provided...`
+
+    }else if (process.argv[2] === "plus"){
+        for (let i = 3 ; i < process.argv.length; i++) {
+            total += Number(process.argv[i]) 
+        }
+    }else if (process.argv[2] === "minus"){
+        total = Number(process.argv[3]);
+        for (let i = 4 ; i < process.argv.length; i++ ){
+            total -= Number(process.argv[i])
+        }
+
+   }else {
+    return `Invalid operation: ${process.argv[2]}`
+   }
+   return total;
+
+}
 
 // Don't change anything below this line.
 module.exports = calculator;
diff --git a/package-lock.json b/package-lock.json
index 99b1c39..ce6f0ea 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": {