Implementing Interfaces

1. Create a PaymentMethod interface with:
   • pay(amount: number): string
2. Create and export a CreditCard class that implements PaymentMethod:
   • Public field: cardNumber (string)
   • Constructor (cardNumber: string)
   • pay(amount) returns exactly: Paid $${amount} with credit card ${cardNumber}
3. Create and export a PayPal class that implements PaymentMethod:
   • Public field: email (string)
   • Constructor (email: string)
   • pay(amount) returns exactly: Paid $${amount} with PayPal ${email}
4. Export the classes: export { CreditCard, PayPal } (PaymentMethod itself does not need to be exported)

Fixtures and success criteria

const creditCard = new CreditCard('1234-5678-9012-3456')
const paypal = new PayPal('user@example.com')

• creditCard.cardNumber === '1234-5678-9012-3456'
• creditCard.pay(100) === 'Paid $100 with credit card 1234-5678-9012-3456'
• paypal.email === 'user@example.com'
• paypal.pay(50) === 'Paid $50 with PayPal user@example.com'
• Both instances expose a callable pay method