Rosa is filling up the back of her dump truck with cedar mulch for a delivery to a landscaped shopping center. the mulch is being pumped into the truck. after 30 minutes, the truck is 75% full and weighs 33 tons. fifteen minutes later, rosa's truck is fully loaded and weighs 42 tons. if rosa's truck weighs 15 tons when it is empty, what was the rate in tons per minute that the mulch pump took to load the truck?
a. 0.6 tons per minute
b. 0.93 tons per minute
c. 1.07 tons per minute
d. 1.67 tons per minute