The schools newspaper staff is selling cookies to raise money for the next school year. the first student who sells 252 boxes earns a laptop. eva sells on average 7 boxes per hour, while Sylvia sells on average 3 boxes every 30 minutes. How much time, in hours, will pass until at least one of the students sells enough boxes to earn a laptop?
A.) 10
B.) 15
C.) 23
D.) 36
E.) 42