As Tcp is byte streamed protocol it means we numbered each byte transmitted.
Here Sequence field is 32 bits, So we can uniquely numbered or identify =232 Bytes
Bandwidth is 100 Mbps.
Means 100 Mb data is transmitted in 1 sec
(108 )/8 byte data is transmitted in 1 sec
1 byte data is transmitted in 8/108 sec
232 byte data is transmitted in (232 *8)/108 sec=235/108 seconds
Solving it you will get 343.597 seconds