Beancount 记账有办法在卖出时以均价计收入吗?

假设有如下操作

1. 借 10K CNY 贷 10K CNY (0.05%利, 结算不计小数)
2. 支 2K CNY 租金
3. 以 100 CNY 购入货物 * 50
4. 以 150 CNY 购入货物 * 50
5. 以 200 CNY 出售货物 * 30
6. 以 180 CNY 出售货物 * 70
7. 还 10K CNY 借 10K CNY 贷 & 利息

运费每次记为 200 CNY

这么写是正确的

1970-01-01 open Liabilities:Payable         ;借钱
1970-01-01 open Liabilities:Bank            ;银行贷款
1970-01-01 open Assets:Cash                 ;现金
1970-01-01 open Assets:Tangibles            ;实体资产
1970-01-01 open Expenses:Rent               ;仓库租金
1970-01-01 open Expenses:Traffic            ;运输费用
1970-01-01 open Expenses:Loan:Interest      ;利息
1970-01-01 open Income:Trade                ;交易获利
2000-01-01 * "借贷"
  Liabilities:Payable                                -10000 CNY
  Liabilities:Bank                                   -10000 CNY
  Assets:Cash                                         20000 CNY

2000-01-02 * "租金"
  Expenses:Rent                                        2000 CNY
  Assets:Cash                                         -2000 CNY

2000-01-03 * "购入"
  Expenses:Traffic                                      200 CNY
  Assets:Tangibles                                       50 STH {100 CNY}
  Assets:Cash                                         -5200 CNY

2000-01-04 * "购入"
  Expenses:Traffic                                      200 CNY
  Assets:Tangibles                                       50 STH {150 CNY}
  Assets:Cash                                         -7700 CNY

2000-01-05 * "卖出"
  Expenses:Traffic                                      200 CNY
  Assets:Tangibles                                      -30 STH {100 CNY} @ 200 CNY
  Income:Trade                                        -3000 CNY
  Assets:Cash                                          5800 CNY

2000-01-06 * "卖出"
  Expenses:Traffic                                      200 CNY
  Assets:Tangibles                                      -70 STH {} @ 180 CNY
  Income:Trade                                        -3100 CNY
  Assets:Cash                                         12400 CNY

2000-01-07 * "还"
  Assets:Cash                                        -10000 CNY
  Liabilities:Payable                                 10000 CNY

2000-01-07 * "还"
  Assets:Cash                                        -10030 CNY
  Liabilities:Bank                                    10000 CNY
  Expenses:Loan:Interest                                 30 CNY


;断言检查对账
2000-01-08 balance Assets:Cash                         3270 CNY

但是第五天如果写成下面的格式, 就寄了

2000-01-05 * "卖出"
  Expenses:Traffic                                      200 CNY
  Assets:Tangibles                                      -30 STH {} @ 200 CNY
  Income:Trade
  Assets:Cash                                          5800 CNY

有没有语法或者插件可以实现按照当前平均持有成本出售?

PS: 没学过会计学, 会不会是我理解有问题, 就是应该按照购入价区分来算利润呢?