Below is an instruction that describes a task. Write a response that appropriately completes the request in Swahili. Please answer in Swahili.

### Instruction:
A new book sold 15 copies at the bookstore on Wednesday. On Thursday the book sold three times that many copies. On Friday the book sold one-fifth the number of copies it did on Thursday. How many copies of the book did the bookstore sell by Friday?

### Response:
 Siku ya Alhamisi, kitabu kiliuzwa mara tatu ya idadi hiyo iliyouzwa siku ya Jumatano, ambayo ni mara 3 ya nakala 15 = 15*3 = <<15*3=45>>45.
Siku ya Ijumaa, kitabu kiliuzwa sehemu ya tano ya idadi ya nakala iliyouzwa siku ya Alhamisi, ambayo ni 45/5 = <<45/5=9>>9 nakala.
Hivyo duka la vitabu liliuza nakala 15 + 45 + 9 = <<15+45+9=69>>69 za kitabu ifikapo Ijumaa.