def waste_tyre_price(quality, category):
    if quality not in {'good', 'poor', 'worst'}:
        return "Invalid quality"
    
    if category == 'truck':
        if quality == 'good':
            return 1000
        elif quality == 'poor':
            return 900
        elif quality == 'worst':
            return 800
    elif category == 'car':
        if quality == 'good':
            return 700
        elif quality == 'poor':
            return 600
        elif quality == 'worst':
            return 500
    elif category == 'bike':
        if quality == 'good':
            return 480
        elif quality == 'poor':
            return 380
        elif quality == 'worst':
            return 280