The Salinas brothers, Juan and Carlos, have collected pledges for a bike rally they plan to have to raise money for their boy scout troop. Carlos's pledges total $11.50/mi and Juan's pledges total $9.75/mi. Carlos can peddle 10 mi/hr and Juan can peddle 12 mi/hr. If they plan to start and stop at the same time, how many hours will they have to bike if they want to raise at least $1000 together?