On Poverty Row, many Bs were made on budgets that would have barely covered petty cash on a major's A film, with costs at the bottom of the industry running as low as $5,000. By the mid-1930s, the double feature was the dominant U.S. exhibition model, and the majors responded. In 1935, B movie production at Warner Bros. was raised from 12 to 50% of studio output. The unit was headed by Bryan Foy, known as the "Keeper of the Bs". At Fox, which also shifted half of its production line into B territory, Sol M. Wurtzel was similarly in charge of more than twenty movies a year during the late 1930s.