#### Answer

a)0.9 b)0.00513

#### Work Step by Step

a) We know that $probability=\frac{number \ of \ good \ outcomes}{number\ of\ all\ outcomes}$, hence $probability=\frac{2518-252}{2518}=0.9.$ b)Two events are dependent, if the outcome of one effects the outcome of the other. Here the events are independent, because the sampling was done with replacement, also $probability=\frac{number \ of \ good \ outcomes}{number\ of\ all\ outcomes}$, hence $probability=\left (\frac{2518-252}{2518}\right )^{50}=0.00513.$