IP header is given as :- 4500 003C 1C46 4000 4017 C311 ACA8 0101 ACA8 0102
Checksum is = C311
To calculate checksum of given header. Add in chunks of 16 bit excluding header checksum
4500 + 003C + 1C46 + 4000 + 4017 +ACA8 + 0101 + ACA8 + 0102 = 23CEC
Here 2 is carry, so add it again = 3CEC + 2 = 3CEE
Now add it with checksum = 3CEE + C311 = FFFF
now flip every bit = 0000
That means no error