Answer:
Use the explantion to answer your question
Step-by-step explanation:
Amount he paid for first 20 shares
= $25 + (20 x $10.51)
= $25 + $210.20
= $235.20
Amount he paid for next 20 shares
= $25 + (20 x $8.93)
= $25 + $178.60
= $203.60
Thus, total amount paid
= $235.20 + $203.60
= $438.80
The sum is 160/(1-r)=1280 where r is the common ratio,
1/(1-r)=1280/160=8
Inverting we get 1-r=1/8, r=7/8.