Kimie is saving some money in her bank account for a holiday. At the start of the year she has ¥x in her bank account. By the end of the year she has ¥200 less than four times the amount she had at the start of the year.

a. Write an expression, in terms of x, for the amount of money Kimie has in her bank account at the end of the year.

b. If Kimie has ¥19 800 at the end of the year, calculate how much money she had in her bank account at the start of the year.