$10.$ Two actors $($each has a mass of $80$ kg $)$ in a space movie rotate in outer space, each holding one end of a $50$ m rope. The two make one complete orbit around the central point between them every $4$ s $.$ What is the tension in the rope?

a$)2\mathrm{.}9$ kN

b$)4\mathrm{.}9$ kN

c$)6\mathrm{.}9$ kN

d$)8\mathrm{.}9$ kN