远期合约价值

def solve(spot_price, risk_free_rate, time_to_maturity, delivery_price):
    import math
    forward_value = spot_price - delivery_price * math.exp(-risk_free_rate * time_to_maturity)
    return {"现货价格": spot_price, "交割价格": delivery_price, "远期价值": round(forward_value, 2)}