What is the theoretical yield of C6H5Br if 42.1g of C6H6 react with 73.0g of Br2?

how do you calculate the theoretical yield?
and
why is the molar mass 0f Br2 73.0g instead of 160g(using the rounded periodic table)?

An athlete swings a ball, connected to the end of a chain, in a horizontal circle. the athlete is able to rotate the ball at the rate of 8.13 rev/s when the length of the chain is 0.600 m. when he increases the length to 0.900 m, he is able to rotate the ball only 6.04 rev/s. (a) which rate of rotation gives the greater speed for the ball? 6.04 rev/s 8.13 rev/s (b) what is the centripetal acceleration of the ball at 8.13 rev/s? m/s2 (c) what is the centripetal acceleration at 6.04 rev/s? m/s2