Hong Kong Book Fair Part 2 + Chinese Calligrapgy

I usually go to Hong Kong Book Fair twice a year. I met a student couple this morning. I like this couple very very much!!!!!!! The boy student has a great talent for drawing. The girl student is smart and outspoken. I'm very happy that they're coming together. Last year, the boy student deferred his study and went to mainland China for a one-year internship.

Today, my friend broke her promise. She said she would come to Book Fair WITH ME!!!!! However, she need to practice executing Chinese Calligraphy, so she didn't come at last.
I still met her this afternoon(She showed what she wrote this morning), because we planned to celebrate my friend, Samu's birthday in a Japanese restaurant in Wan Chai. We tried many fresh SASHIMI, including Pacific Saury(秋刀魚), Echinoida(海膽), Jelly Fish(水母), Beef, Baby Eel(鰻魚), Belly of Swordfish(劍魚腩) and two starters(bean curd and squid) PLUS one bean curd cheese cake. I was TOTALLY FULL!!!!!











Can you guess how much is this FRESH lunch?
Let me give you some hints!!
It's over $1000, and ABCD are 4 different numbers which indicate the amount shown in the bill.

Equation 1: AB = 2*CD
Equation 2: 7*B = CD
Equation 3: (a+C)*D = CB
Equation 4: 2*C = B