How much does the school have to charge for each candy bar to make a profit of 10 dollars per box?

The complete question is
A school purchases boxes of candy bars. 
• Each box contains 50 candy bars. 
• Each box costs $30. 
How much does the school have to charge for each candy bar to make a profit of 
$10 per box?

step 1
charge for each box $10
so
the new box cost $10+$30=$40

step 2
divide the new box cost to total candy bars
$40/50=$0.80 

the answer is
 the school have to charge for each candy bar $0.80