Answer:
Total time taken = 0.62 seconds 
Step-by-step explanation:
Transmission rate = 18 Mbps
The size of file X winch will go fast= 11.73 MiB (Mebibyte) = 8.38 Mb(Megabit) 
The time it will take to transfer = File size / Transmission rate 
 = 8.38 / 18 seconds 
 = 0.46 seconds 
Mb in 1 KiB = 116.415 
The file Y that will go next has size = 340 Kib
 = 340 / 116.41 Mb 
 = 2.92 Mb 
The time it will take to transfer = 2.92 / 18 seconds
 = 0.16
Total time = Time taken for file X + Time taken for file Y 
= 0.46 + 0.16 
= 0.62