Number of samples - how to calculate it?

Hello everybody! I am writing a code to play DTMF tones, and need to play them for 0.5 seconds. My question is: how to calculate the number of samples [n]? I tried to apply fs/f0 but the result was a small range. I am using FS = 8000 Hz. Thank you!!!

fs = 8000; 

% Below I tried to use 5000 just for testing my code, and worked well:       
n = [0:5000];

tone0 = (1.5)*cos(0.73906*n)+(1.5)*cos(1.04929*n);

Answer 1

[dpb]

8000 Hz --> 8000 samples/sec * 0.5 sec --> 4000 samples