Why is that the answer E is equivalent to 3s(18) + 5s(11) - 3s(6)

EXAMPLE 4 Which of the following is a correct expression for the accumulated value, on the date of the last payment, of 3 paid in years 1 to 7, 8 paid in years 8 to 12 and 5 paid in years 13 to 18? (A) 35781 +58721 383 (B) 357(1+i) 10 + 853(1+i)* + 553 (C) 3873 +8s+5sa (D) 35781 + 5511 - 383 (E) 357(1 + i)!! +883(1+i) +55a SOLUTION Answer (E). Using the block payment" approach, a correct answer would also be 35781 + 5571- 352