Final answer:
The cost function for producing lawnmowers, denoted as C(x), is found by subtracting the profit function from the revenue function. The calculation results in the cost function C(x)=60x+200, which corresponds to option B.
Step-by-step explanation:
The company's cost function is determined by subtracting the profit function from the revenue function, as profit is defined as total revenue minus total cost. We are given the revenue function R(x)=90x-x² and the profit function P(x)=-x²+30x-200. To find the cost function, C(x), we rearrange the profit equation to be P(x)=R(x)-C(x), which yields C(x)=R(x)-P(x). Substituting the given functions into this equation results in C(x)=(90x-x²)-(-x²+30x-200) simplifying to C(x)=90x-x²+x²-30x+200, which then simplifies further to C(x)=60x+200. Therefore, the correct answer is B. C(x)=60x+200.