tax question

fazilla catering is a vat registered business, john ordered buffer for his birthday with the following item:
price per person:$20 pax
number of people:40
trade discount:15%
term of payment :60 days net 3/07 2% penalty for late payment.
what is the amount of VAT to be charged on this invoice?
A $104.52
B $119
C$115.43
D$140.00

• Q3 what is the total amount payable by john on the invoice,if he settle the invoice on the 55th days from the invoice day.
A $799
B $775.03
C $778.60
D $795.43
i have no idea how to do…this part.
Q4 what is the amount to be paid by john if he pay on the 4th day of the invoice?
A $799
B $775.03
C $778.60
D $795.63
Q5 what is the amount to be paid by john if he pay after the due date?
A $799
B $795.43
C $778.60
D $809.63