Please help with the parts I got wrong (highlighted)

Partner Retirement: Various Cases The capital balances for the partnership of Diaz, Isidro, and Nelson are as follows: The partners share income in a1:3:6 ratio. Nelson decides to retire. Diaz and Isidro continue the partnership, sharing income in a 1:3 ratio. Required Prepare the journal entry or entries to record the retirement of Nelson in each of the following scenarios: a. Diaz and Isidro use their personal assets to buy Nelson's interest for $600,000. c. Same as b., but the partial goodwill approach is used. d. Same as b., but the total goodwill approach is used