What is the dividend yield on stock A that sells at 15$/share, when company A pays a quarterly dividend of $0.10 per share?

Given:

Let P= profit
let n= no. of tacos sold per day

Sol'n:

P= 3.25n-210
the profit needs to be positive, thus

3.25n>210

n>210/3.25

n> 64.615

they can only sell whole tacos, therefore they must sell at least 65 tacos to make a profit and that profit is:

P=3.25n-210

P=3.25*65 - 210

P= 211.25 -210

P= 1.25

$1.25 profit