Astring trimmer is a tool for cutting grass and weeds; it utilizes a length of nylon

r = 22.3 cm

Explanation:

given,

angular speed = 45 rev/s

tangential speed  = 63 m/s

length of the rotating string

angular velocity =

ω = 2 π N

ω = 2 π x 45

ω = 282.74 rad/s

we know,

v = r ω

r = 22.3 cm

Oracio is the most cost-effective choice because he would cost the least to complete the project. However, he would also take the longest amount of time. Camilla could complete the job the fastest, but she costs more than Oracio. SciTech will have to decide if it is more important to save money or complete the work quickly to meet the deadline.  

Hope this helps :)