Answer:
Option C: 126
Step-by-step explanation:
Total displays to be assembled = 280
25% of the displays are assembled during the first hour, this value becomes:
[tex]0.25\times280=70[/tex]
Remaining displays = [tex]280-70=210[/tex]
40% of the remaining displays during the second hour, the value becomes:
[tex]0.40\times210=84[/tex]
Hence, number of displays that will not have been assembled by the end of the second hour = [tex]210-84=126[/tex]
Therefore, the answer is 126.