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

### Instruction:
Mia has 4 times as many shells as David. Ava has 20 more shells than Mia. Alice has half the number of shells Ava has. If David has 15 shells, what the total number of conch shells they all have?

### Response:
 Ikiwa David ana makombe 15, na Mia ana makombe mara 4 ya makombe ya David, basi Mia ana makombe 15*4 = <<15*4=60>>60.
Ava ana makombe 20 zaidi ya Mia, hivyo ana makombe 60+20 = 80.
Alice ana nusu ya idadi ya makombe Ava ana, hivyo ana makombe 1/2*80 = 40.
Kwa pamoja, wote wana makombe 15+60+80+40 = <<15+60+80+40=195>>195.