What is the answer? kim and cyndi are starting a business tutoring students in math. they rent an office for $400 per month and charge $40 per hour per student. if they have 15 students each for one hour per week how much profit do they make together in a month?

So
400 is the first cost
profit=x-400
40 per student (each student=1 hour)
x=students, since hour=1
40 times x
profit=40x-400
15 students per week
so
profit per week=40(15)-400
profit per week=600-400
profit per week=200

1  month is about 4 weeks so
200 times 4=800
they  make 800 a month

What mathematical statement is missing ? ? the answer is b