Based on the information below, how many Clash rackets should Rackets Inc. produce during the

period?

Rackets Inc. makes three different types of tennis rackets. Each racket

needs a special machine to put the frame together, and the machine

can only run $210$ hours during the period. Below is information on each

type of racket:

For the period, the demand for Blade rackets is $300,$ the demand for

Clash rackets is $350,$ and the demand for Ultra rackets is $150.$

The Correct answer is $40,$ I do not know how they got it$?$