For a science project, professor lucero asked each one of her students to measure the amount of gas their parents use to take them to school each week. the students measured the amount of gas in tank fractions. jamal used 5/16 of a tank, micaela used 3/16 of a tank, pedro used 3/8 of a tank, franco used 5/8 of a tank and kristel used 1/4 of a tank.
a. how much gas did they use in total?
b. if one gas tank costs $40, how much less did kristel spend then pedro?