A sender needs to send the four data items Ox3456, OxABCC, Ox02BC, and OxEEEE. Answer the following: a. Find the checksum at the sender site. b. Find the checksum at the receiver site if there is no error. c. Find the checksum at the receiver site if the second data item is changed to OxABCE. d. Find the checksum at the receiver site if the second data item is changed to OxABCE and the third data item is changed to Ox02BA.