def find_ask(asks, t_depth: float):
    """find best ask in the orderbook needed to fill an order of amount t_depth"""
    price = 0.0
    depth = 0.0
    for a in asks:
        price = float(a['price'])
        depth += float(a['amount'])
        if depth >= t_depth:
            break
    
    return round(price + 0.000001, 7)