Step-by-step explanation:
let's assume one month is 30 days you would multiply 10 by 30.

which would be 300 hours in 1 month
now if one month is 31 days you would simply multiply 10 by 31.

which would be 310 hours
You’re gonna do 3500X3X3 = 31500
The correct answer is :

Just it....
And we're done.
Thanks for watching buddy good luck.
♥️♥️♥️♥️♥️
Agreed I believe it’s c as well