Question 1039790
Probability there are 0=0.9^17=0.1668
there is 1= 17*.9^16*.1, which is 17C1(0,9)^16*(0.1)^1=0.3150
there are 2=17C2(0.9)^15(0.1)^2=0.2800; 17C2= 17*16/2=136
The probability is their sum, or 0.7618.  
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Analogous for 0.85
.85^17=0.0631
17(.85^16)(.15^1)=0.1893
136*(.85^15)(.15^2)=0.2673
This sum is 0.5197.  It is less, as it should be because there is a higher probability of defective pens and 0,1,2 defects will have a lower probability.
it is nCk(p)^(n-k)*(1-p)^k