13. Sam is playing a computer game.
When Sam earns a reward in the game, she randomly receives either a Silver reward or a Gold reward.
Each time that Sam earns a reward, the probability of receiving a Gold reward is 0.4 One day Sam plays the computer game and earns 11 rewards.
- Find the probability that she receives
- exactly 2 Gold rewards,
- at least 5 Gold rewards.
In the next month Sam earns 300 rewards.
She decides to use a Normal distribution to estimate the probability that she will receive at least 135 Gold rewards.
- Find the mean and variance of this Normal distribution.
- Estimate the probability that Sam will receive at least 135 Gold rewards.
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