<span>a. find the number of units of tacos she must sell to minimise her cost. </span>to find a minimum we need to find the function derivative and make it equal to zero: dc/dx = 2x - 40 = 0 2x = 40 x = 20 therefore to minimize the cost, she needs to sell 20 units of tacos
<span>b. find the minimum cost. </span>that can be done by substituting the previous result, 20 tacos, in the original equation: <span>C(x) = x^2 - 40x + 610 </span>C(20) = (20)^2 - 40(20) + <span>610 </span>= 400 - 800 + 610 = 210 the minimum cost will be 210 dollars
