模考软件中的数学题，请教

1。A computer chip manufacturer expects the ratio of the number of defective chips to the total number of chips in all future shipments to equal the corresponding ratio for shipments S1,S2,S3, and S4 combined, as shown in the table above. What is the expected number of defective chips in a shipment of 60,000 chips?

A 14

B 20

C 22

D 24

E 25

2。For one toss of a certain coin, the probability that the outcome is heads is 0.6. If this coin is tossed 5 times, which of the following is the probability that the outcome will be heads at least 4 times?

(0.6)⁵

2(0.6)⁴

3(0.6)⁴(0.4)

4(0.6)⁴(0.4)+ (0.6)⁵

5(0.6)⁴(0.4)+ (0.6)⁵

^{这两题怎么解啊，第一题不大理解题意。 谢谢啊！缘分啊！}

1.OG给出的答案为：

（2＋5＋6＋4）/(5,000+12,000+18,000+16,000)=N/60,000

N=20 我也不知道为什么，讨论……

2.选E吧？

   至少四次正面，即分为刚好四次正面和五次全正面，则

  概率为： C(4,5)(0.6)⁴(0.4)+(0.6)⁵⁼5(0.6)⁴(0.4)+ (0.6)⁵