I need help with #1 #3 #4

Instructions and Homework
        GL Accountant Homework
        Instructions
        1) When reviewing AP for month end close, you discover that an invoice for Business Insurance dated 7/28/2020-8/27/2020 in the amount of $50,400 was expensed. This expense was allocated across all departments. The standard allocation procedure is that the support and operations departments do not receive any of the cost. 
            a) Amortize straight line, using exact days.
            b) How much was the cost to Engineering overstated? What should be the correct prepaid balance for this cost?
                        a) amortisation of expenses                            b) Calculation of overstated cost
        XYZ Month End Date: 8/1/2020                    Allocation basis    Expense    Prepaid    Total                Allocation basis    Expense    Revised     Cost overstated
        Prepaid Threshold: $2500                No. of days        5    26    31
                        Total amount to be allocated        8,129    42,271    50,400            Total amount wrogly allocated        50,400
        Headcount:
        Engineering - 329                Engineering - 329    329    2,334    12,135                Engineering - 329    329    14,469    2,334    12,135
        Sales - 637                Sales - 637    637    4,518    23,496                Sales - 637    637    28,015
        Support - 28                Marketing - 56    56    397    2,066                Marketing - 56    56    2,463
        Operations - 7                G&A - 124    124    880    4,574                G&A - 124    124    5,453
        Marketing - 56                Total expenses    1146    8,129    42,271                Total expenses    1146    50,400
        G&A - 124                The amortisation will be $8,129 as per above table. There will be no allocation to support and operations.                            The overstated costs for engineering is $12135 and the correct balance of prepaid will also be $12135 in table 1
        2) Please refer to "Excel Test" tab for the excel related test.
        3) Please explain the GL impact of the sales transaction noted on the "Invoice Sample" tab, including impact on the (i) transaction date, (ii) customer payment date, and (iii) upon filing of a tax return with a taxing authority.
        Solution
        i) On transaction sales sales revenue account and GST collected on sales will be credited by $100 and $8.50 respectively and Accounts receivables GL will be debited by $108.50
        ii) On Customer payment date Cash account will be debited and Accounts...