The following data pertains to activity and costs for two months: june july activity level in 10,000 12,000 direct materials $16,000 $ ? fixed factory rent 12,000 ? manufacturing overhead 10,000 ? total cost $38,000 $42,900 assuming that these activity levels are within the relevant range, the manufacturing overhead for july was: a) $10,000 b) $11,700 c) $19,000 d) $9,300