Решение
(8.3.1.2.1)
(8.3.1.2.2)
![S[?] = `*`(500, .4)](images/e_41.gif){kind=small}
![S[?] = 200.0](images/e_42.gif){kind=small}
![S[:] = `+`(180, `*`(.3, `*`(`+`(500, -400))))](images/e_43.gif){kind=small}
![S[:] = 210.0](images/e_44.gif){kind=small}
![S[1] = 245](images/e_45.gif){kind=small}