diff --git a/src/index.js b/src/index.js
index ac593f4..678521d 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,11 +1,55 @@
 // Entry
-class Entry {}
+class Entry {
+  constructor(date, amount, description) {
+    this.date = date;
+    this.amount = amount;
+    this.description = description;
+  }
+  getFormattedAmount() {
+    return `${this.amount} €`;
+
+  }
+}
 
 // Income
-class Income {}
+class Income extends Entry {
+  constructor(date, amount, description) {
+    super(date, amount, description);
+    this.type = "income";
+  }
+}
 
 // Expense
-class Expense {}
+class Expense extends Entry {
+  constructor(date, amount, description, paid) {
+    super(date, amount, description);
+    this.paid = paid;
+    this.type = "expense";
+  }
+  getFormattedAmount() {
+    return `-${this.amount} €`;  // Override to include the minus sign
+  }
+}
 
 // Budget
-class Budget {}
+class Budget {
+    constructor(){
+        this.entries = [];
+    }
+    addEntry(newEntry){
+        this.entries.push(newEntry)
+    }
+    getCurrentBalance(){
+        let total = 0;
+        for(let i = 0; i<this.entries.length; i++){
+            const currentEntry= this.entries[i];
+            if(currentEntry.type === 'income'){
+                total += currentEntry.amount;
+            }
+            else if (currentEntry.type === 'expense'){
+                total -= currentEntry.amount;
+            }
+        }
+        return total;
+    }
+}