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

### Instruction:
A shop is offering a discount on pens. If you buy 10 pens at the regular price, you can get the next 10 for half off. A customer came in and bought 20 pens for $30. What's the regular price of one pen in dollars?

### Response:
 Hebu p iwe gharama ya kalamu moja ya kawaida.
Tunajua kuwa kalamu 10 za kwanza zinanunuliwa kwa bei ya kawaida, hivyo zinagharimu 10*p.
Pia tunajua kuwa kalamu zozote zinazonunuliwa baada ya kalamu 10 za kwanza zinagharimu (20 kalamu - 10 kalamu) * p/2.
Tukiongeza gharama ya kalamu 10 za kwanza na kalamu zinazouzwa kwa nusu ya bei, tunapata jumla ya ununuzi wa bei ya $30=10*p + (20-10)*p/2.
Hii inafanya 10*p + 10 *p/2 = $30.
Hivyo, tunachanganya vipengele kama na kupata 10*p + 5*p = $30.
Hivyo, $30 = 15* p.
Hatimaye, p=$2.