交易性金融资产公允价值变动

def solve(cost, fv_beginning, fv_ending):
    fv_change = fv_ending - fv_beginning
    total_gain = fv_ending - cost
    return {"成本": cost, "期初公允价值": fv_beginning, "期末公允价值": fv_ending, "本期公允价值变动": fv_change, "累计损益": total_gain}