y=mx+b
since the variable that will increase or deacrease is the number of books
then we set it to x
x=number of books
the member fee is constant so
b=10
the amount of money will increase by 5.99 per book so
m=5.99
the total amount of money will be our function since it depends on x
y=total amount of money
y=5.99x+10
total amount of money=5.99(number of books)+membership fee
